def index_first_char_not_equal_to(value: str, char: str, start_index: int = 0) -> int:
  """Returns the index of the first character in string 'value' not containing the character provided by 'char' starting at index start_index."""
  for i in range(start_index, len(value)):
    if value[i] != char:
      return i
  return -1