code: def delete_metadata_at_key(self, key):
          
          j, r = self.datacenter.request('DELETE', self.path + '/metadata/' + 
                      key)
          r.raise_for_status()
          return self.get_metadata()
docs: ::
          
              DELETE /:login/machines/:id/metadata/:key
          
          :param key: identifier for matadata entry
          :type key: :py:class:`basestring`
          
          :Returns: current metadata
          :rtype: :py:class:`dict`
          
          Deletes the machine metadata contained at 'key'. Also explicitly 
          requests and returns the machine metadata so that the local copy stays 
          synchronized.