docs: def extract_docstring_summary(docstring):
      """Get the first summary sentence from a docstring.
  
      Parameters
      ----------
      docstring : `list` of `str`
          Output from `get_docstring`.
  
      Returns
      -------
      summary : `str`
          The plain-text summary sentence from the docstring.
      """
      summary_lines = []
      for line in docstring:
          if line == '':
              break
          else:
              summary_lines.append(line)
      return ' '.join(summary_lines)