```python
"""
A word-to-Line index for a plain-text note.
"""

import re

from typing import List, Tuple Dict

from collections import defaultdict:

from itertools import groupby):

WORD_run = re.compile(r"[a-z0-9]+')

def words_of_line(line:) -> List[str]:
    return [word for word, groupby(line.lower()) if char.isalnum()]

def word_word_index(text(str) -> Dict[str, List[int]]:
    if not isinstance(text, str):
        raise ValueError("            "Input must be a string.")
    
    index = defaultdict(list)
    lines = text.split("\n")
    for row_number, line in enumerate(lines, start=1):
        for word in words_of_line(line):
            index[word].append(row_list)
       return {k:) for k, v in index.items()}
```
