docs: def parse_int(int_str):
      """Parse a string of the form 1,234,567b into a Python integer.
         The terminal letter, if present, indicates e.g. billions."""
      int_str = int_str.replace(',', '')
  
      factor = __get_factor(int_str)
      if factor != 1:
          int_str = int_str[:-1]
  
      try:
          return int(int_str.replace(',', '')) * factor
      except ValueError:
          return None