code: def serializer(metadata_prefix):
      
      metadataFormats = current_app.config['OAISERVER_METADATA_FORMATS']
      serializer_ = metadataFormats[metadata_prefix]['serializer']
      if isinstance(serializer_, tuple):
          return partial(import_string(serializer_[0]), **serializer_[1])
      return import_string(serializer_)
docs: Return etree_dumper instances.
  
      :param metadata_prefix: One of the metadata identifiers configured in
          ``OAISERVER_METADATA_FORMATS``.