code: def _get_definitions(source):
      # type: (str) -> Tuple[Dict[str, str], int]
      
      max_len = 0
      descs = collections.OrderedDict()  # type: Dict[str, str]
      lines = (s.strip() for s in source.splitlines())
      non_empty_lines = (s for s in lines if s)
      for line in non_empty_lines:
          if line:
              arg, desc = re.split(r'\s\s+', line.strip())
              arg_len = len(arg)
              if arg_len > max_len:
                  max_len = arg_len
              descs[arg] = desc
      return descs, max_len
docs: Extract a dictionary of arguments and definitions.
  
      Args:
          source: The source for a section of a usage string that contains
              definitions.
  
      Returns:
          A two-tuple containing a dictionary of all arguments and definitions as
          well as the length of the longest argument.