code: def _best_fit_font_size(self, family, max_size, bold, italic, font_file):
          
          if font_file is None:
              font_file = FontFiles.find(family, bold, italic)
          return TextFitter.best_fit_font_size(
              self.text, self._extents, max_size, font_file
          )
docs: Return the largest integer point size not greater than *max_size*
          that allows all the text in this text frame to fit inside its extents
          when rendered using the font described by *family*, *bold*, and
          *italic*. If *font_file* is specified, it is used to calculate the
          fit, whether or not it matches *family*, *bold*, and *italic*.