code: def fit_text(self, font_family='Calibri', max_size=18, bold=False,
                   italic=False, font_file=None):
          
          # ---no-op when empty as fit behavior not defined for that case---
          if self.text == '':
              return
  
          font_size = self._best_fit_font_size(
              font_family, max_size, bold, italic, font_file
          )
          self._apply_fit(font_family, font_size, bold, italic)
docs: Fit text-frame text entirely within bounds of its shape.
  
          Make the text in this text frame fit entirely within the bounds of
          its shape by setting word wrap on and applying the "best-fit" font
          size to all the text it contains. :attr:`TextFrame.auto_size` is set
          to :attr:`MSO_AUTO_SIZE.NONE`. The font size will not be set larger
          than *max_size* points. If the path to a matching TrueType font is
          provided as *font_file*, that font file will be used for the font
          metrics. If *font_file* is |None|, best efforts are made to locate
          a font file with matchhing *font_family*, *bold*, and *italic*
          installed on the current system (usually succeeds if the font is
          installed).