code: def deserialize(self, mutagen_value):
          
          if self.suffix and isinstance(mutagen_value, six.text_type) \
             and mutagen_value.endswith(self.suffix):
              return mutagen_value[:-len(self.suffix)]
          else:
              return mutagen_value
docs: Given a raw value stored on a Mutagen object, decode and
          return the represented value.