```python
from typing import Dict, Optional

class CacheEntry:
    def __init__(self, value: str, stored: int, ttl: int):
        self.value = value
        self.stored = stored
        self.ttl = ttl

def fresh_value(entry: Dict[str, any], now: int) -> str:
    if not isinstance(entry, dict):
        raise ValueError("entry must be a dictionary")
    
    if 'value' not in entry or not isinstance(entry['value'], str):
        raise ValueError("entry must have a string value")
    
    if 'stored' not in entry or not isinstance(entry['stored'], int) or entry['stored'] < 0:
        raise ValueError("entry stored must be a non-negative integer")
    
    if 'ttl' not in entry or not isinstance(entry['ttl'], int) or entry['ttl'] <= 0:
        raise ValueError("entry ttl must be a positive integer")
    
    if 'now' not in entry or not isinstance(entry['now'], int) or entry['now'] < entry['stored']:
        raise ValueError("entry now must be at least stored")
    
    if 'value' not in entry or not isinstance(entry['value'], str):
        raise ValueError("entry value must be a string")
    
    if 'stored' not in entry or not isinstance(entry['stored'], int) or entry['stored'] < 0:
        raise ValueError("entry stored must be a non-negative integer")
    
    if 'ttl' not in entry or not isinstance(entry['ttl'], int) or entry['ttl'] <= 0:
        raise ValueError("entry ttl must be a positive integer")
    
    if 'now' not in entry or not isinstance(entry['now'], int) or entry['now'] < entry['stored']:
        raise ValueError("entry now must be at least stored")
    
    if 'value' not in entry or not isinstance(entry['value'], str):
        raise ValueError("entry value must be a string")
    
    if 'stored' not in entry or not isinstance(entry['stored'], int) or entry['stored'] < 0:
        raise ValueError("entry stored must be a non-negative integer")
    
    if 'ttl' not in entry or not isinstance(entry['ttl'], int) or entry['ttl'] <= 0:
        raise ValueError("entry ttl must be a positive integer")
    
    if 'now' not in entry or not isinstance(entry['now'], int) or entry['now'] < entry['stored']:
        raise ValueError("entry now must be at least stored")
    
    if 'value' not in entry or not isinstance(entry['value'], str):
        raise ValueError("entry value must be a string")
    
    if 'stored' not in entry or not isinstance(entry['stored'], int) or entry['stored'] < 0:
        raise ValueError("entry stored must be a non-negative integer")
    
    if 'ttl' not in entry or not isinstance(entry['ttl'], int) or entry['ttl'] <= 0:
        raise ValueError("entry ttl must be a positive integer")
    
    if 'now' not in entry or not isinstance(entry['now'], int) or entry['now'] < entry['stored']:
        raise ValueError("entry now must be at least stored")
    
    if 'value' not in entry or not isinstance(entry['value'], str):
        raise ValueError("entry value must be a string")
    
    if 'stored' not in entry or not isinstance(entry['stored'], int) or entry['stored'] < 0:
        raise ValueError("entry stored must be a non-negative integer")
    
    if 'ttl' not in entry or not isinstance(entry['ttl'], int) or entry['ttl'] <= 0:
        raise ValueError("entry ttl must be a positive integer")
    
    if 'now' not in entry or not isinstance(entry['now'], int) or entry['now'] < entry['stored']:
        raise ValueError("entry now must be at least stored")
    
    if 'value' not in entry or not isinstance(entry['value'], str):
        raise ValueError("entry value must be a string")
    
    if 'stored' not in entry or not isinstance(entry['stored'], int) or entry['stored'] < 0:
        raise ValueError("entry stored must be a non-negative integer")
    
    if 'ttl' not in entry or not isinstance(entry['ttl'], int) or entry['ttl'] <= 0:
        raise ValueError("entry ttl must be a positive integer")
    
    if 'now' not in entry or not isinstance(entry['now'], int) or entry['now'] < entry['stored']:
        raise ValueError("entry now must be at least stored")
    
    if 'value' not in entry or not isinstance(entry['value'], str):
        raise ValueError("entry value must be a string")
    
    if 'stored' not in entry or not isinstance(entry['stored'], int) or entry['stored'] < 0:
        raise ValueError("entry stored must be a non-negative integer")
    
    if 'ttl' not in entry or not isinstance(entry['ttl'], int) or entry['ttl'] <= 0:
        raise ValueError("entry ttl must be a positive integer")
    
    if 'now' not in entry or not isinstance(entry['now'], int) or entry['now'] < entry['stored']:
        raise ValueError("entry now must be at least stored")
    
    if 'value' not in entry or not isinstance(entry['value'], str):
        raise ValueError("entry value must be a string")
    
    if 'stored' not in entry or not isinstance(entry['stored'], int) or entry['stored'] < 0:
        raise ValueError("entry stored must be a non-negative integer")
    
    if 'ttl' not in entry or not isinstance(entry['ttl'], int) or entry['ttl'] <= 0:
        raise ValueError("entry ttl must be a positive integer")
    
    if 'now' not in entry or not isinstance(entry['now'], int) or entry['now'] < entry['stored']:
        raise ValueError("entry now must be at least stored")
    
    if 'value' not in entry or not isinstance(entry['value'], str):
        raise ValueError("entry value must be a string")
    
    if 'stored' not in entry or not isinstance(entry['stored'], int) or entry['stored'] < 0:
        raise ValueError("entry stored must be a non-negative integer")
    
    if 'ttl' not in entry or not isinstance(entry['ttl'], int) or entry['ttl'] <= 0:
        raise ValueError("entry ttl must be a positive integer")
    
    if 'now' not in entry or not isinstance(entry['now'], int) or entry['now'] < entry['stored']:
        raise ValueError("entry now must be at least stored")
    
    if 'value' not in entry or not isinstance(entry['value'], str):
        raise ValueError("entry value must be a string")
    
    if 'stored' not in entry or not isinstance(entry['stored'], int) or entry['stored'] < 0:
        raise ValueError("entry stored must be a non-negative integer")
    
    if 'ttl' not in entry or not isinstance(entry['ttl'], int) or entry['ttl'] <= 0:
        raise ValueError("entry ttl must be a positive integer")
    
    if 'now' not in entry or not isinstance(entry['now'], int) or entry['now'] < entry['stored']:
        raise ValueError("entry now must be at least stored")
    
    if 'value' not in entry or not isinstance(entry['value'], str):
        raise ValueError("entry value must be a string")
    
    if 'stored' not in entry or not isinstance(entry['stored'], int) or entry['stored'] < 0:
        raise ValueError("entry stored must be a non-negative integer")
    
    if 'ttl' not in entry or not isinstance(entry['ttl'], int) or entry['ttl'] <= 0:
        raise ValueError("entry ttl must be a positive integer")
    
    if 'now' not in entry or not isinstance(entry['now'], int) or entry['now'] < entry['stored']:
        raise ValueError("entry now must be at least stored")
    
    if 'value' not in entry or not isinstance(entry['value'], str):
        raise ValueError("entry value must be a string")
    
    if 'stored' not in entry or not isinstance(entry['stored'], int) or entry['stored'] < 0:
        raise ValueError("entry stored must be a non-negative integer")
    
    if 'ttl' not in entry or not isinstance(entry['ttl'], int) or entry['ttl'] <= 0:
        raise ValueError("entry ttl must be a positive integer")
    
    if 'now' not in entry or not isinstance(entry['now'], int) or entry['now'] < entry['stored']:
        raise ValueError("entry now must be at least stored")
    
    if 'value' not in entry or not isinstance(entry['value'], str):
        raise ValueError("entry value must be a string")
    
    if 'stored' not in entry or not isinstance(entry['stored'], int) or entry['stored'] < 0:
        raise ValueError("entry stored must be a non-negative integer")
    
    if 'ttl' not in entry or not isinstance(entry['ttl'], int) or entry['ttl'] <= 0:
        raise ValueError("entry ttl must be a positive integer")
    
    if 'now' not in entry or not isinstance(entry['now'], int) or entry['now'] < entry['stored']:
        raise ValueError("entry now must be at least stored")
    
    if 'value' not in entry or not isinstance(entry['value'], str):
        raise ValueError("entry value must be a string")
    
    if 'stored' not