code: def _iter_font_files_in(cls, directory):
          
          for root, dirs, files in os.walk(directory):
              for filename in files:
                  file_ext = os.path.splitext(filename)[1]
                  if file_ext.lower() not in ('.otf', '.ttf'):
                      continue
                  path = os.path.abspath(os.path.join(root, filename))
                  with _Font.open(path) as f:
                      yield ((f.family_name, f.is_bold, f.is_italic), path)
docs: Generate the OpenType font files found in and under *directory*. Each
          item is a key/value pair. The key is a (family_name, is_bold,
          is_italic) 3-tuple, like ('Arial', True, False), and the value is the
          absolute path to the font file.