code: def canonical_extension(fmt_ext):
          
          if MimeType.has_value(fmt_ext):
              return fmt_ext
          try:
              return {
                  'tif': MimeType.TIFF.value,
                  'jpeg': MimeType.JPG.value,
                  'hdf5': MimeType.HDF.value,
                  'h5': MimeType.HDF.value
              }[fmt_ext]
          except KeyError:
              raise ValueError('Data format .{} is not supported'.format(fmt_ext))
docs: Canonical extension of file format extension
  
          Converts the format extension fmt_ext into the canonical extension for that format. For example,
          ``canonical_extension('tif') == 'tiff'``. Here we agree that the canonical extension for format F is F.value
  
          :param fmt_ext: A string representing an extension (e.g. ``'txt'``, ``'png'``, etc.)
          :type fmt_ext: str
          :return: The canonical form of the extension (e.g. if ``fmt_ext='tif'`` then we return ``'tiff'``)
          :rtype: str