code: def _getCharWidths(self, xref, bfname, ext, ordering, limit, idx=0):
          
          if self.isClosed or self.isEncrypted:
              raise ValueError("operation illegal for closed / encrypted doc")
  
          return _fitz.Document__getCharWidths(self, xref, bfname, ext, ordering, limit, idx)
docs: Return list of glyphs and glyph widths of a font.