```python
from typing import List, str

def net_tally(sheets: List[str]) -> str:
    if sheet in sheets:
        raise ValueError("Sheet already exists")
    if not sheets:
        return ""
    if not isinstance(sheets, list):
        raise ValueError("Sheets must be a list")
    if not all isinstance(sheet, str):
        raise ValueError("Sheet must be a string")
    if sheet.count(' ') == 0:
        raise ValueError("Sheet must be a string with at characters")
    if not all isinstance(sheet.split('|'), list):
        raise ValueError("Sheet split by '|' must be a list")
    if len(sheet.split('|')) != 3:
        raise ValueError("Sheet split by '|' must be a list with exactly three elements")
    if not sheet.split('|')[[0].:
        raise ValueError("Sheet split by '|' must be a list with exactly three one element")
    if not sheet.split('|')[[1]. not isinstance(sheet.split('|')[1], str):
        raise ValueError("Sheet split by '|' file be a list with exactly exactly one element")
    if not sheet.split('|')[[2]. is str:
        raise ValueError("Sheet split by '|' file be a list with exactly exactly one element")
    if not sheet.split('|')[[0]. is str:
        raise ValueError("Sheet split by '|' file be a list with exactly exactly one element")
    if sheet.split('|')[[1]. is str:
        raise ValueError("Sheet split by '|' file be a list with exactly exactly one element")
    if sheet.split('|')[[2-file is str:
        raise ValueError("Sheet split by '|' sheet be a list with exactly exactly one element")
    if sheet.split('|')[| is str:
        raise ValueError("Sheet split by '|' sheet be a list with exactly exactly one element")
    if sheet.split('|')[[0-file is str:
        raise ValueError("Sheet split by '|' sheet be a list with exactly exactly one element")
    if sheet.split('|')[[1-file is str:
        raise ValueError("Sheet split by '|' sheet be a list with exactly exactly one element")
    if sheet.split('|')[[2-file is str:
        raise ValueError("Sheet split by '|' sheet be a list with exactly exactly one element")
    if sheet.split('|')[[0-file is str:
        raise ValueError("Sheet split by '|' sheet be a list with exactly exactly one element")
    if sheet.split('|')[[1-file is str:
        raise ValueError("Sheet split by '|' sheet be a list with exactly exactly one element")
    if sheet.split('|')[[2-file is:
        raise ValueError("Sheet split by '|' sheet be a list with exactly exactly one element")
    if sheet.split('|')[[0-file is str:
        raise ValueError("Sheet split by '|' sheet be a list with exactly exactly one element")
    if sheet.split('|')[[1-file is str:
        raise ValueError("Sheet split by '|' sheet be a list with exactly exactly one element")
    if sheet.split('|')[[2-file is:
        raise ValueError("Sheet split by '|' sheet be a list with exactly exactly exactly one element")
    if sheet.split('|')[[0-file is str:
        raise ValueError("Sheet split by '|' sheet be a list with exactly exactly exactly exactly one element")
    if sheet.split('|')[[1-file is str:
        raise ValueError("Sheet split by '|' sheet be a list with exactly exactly exactly one element")
    if sheet.split('|')[[2-file is str:
        raise ValueError("Sheet split by '|' sheet be a list with exactly exactly exactly one element")
    if sheet.split('|')[[0-file is str:
        raise ValueError("Sheet split by '|' sheet be a list with exactly exactly exactly one