def check_ends_with_period(self, definition, docstring):
        """D400: First line should end with a period.

        The [first line of a] docstring is a phrase ending in a period.

        """
        if docstring:
            summary_line = ast.literal_eval(docstring).strip().split('\n')[0]
            if not summary_line.endswith('.'):
                return violations.D400(summary_line[-1])