code: def update_metadata(self, bucket, label, params):
          '''Update the metadata with the provided dictionary of params.
  
          :param parmams: dictionary of key values (json serializable).
          '''
          if self.mode !="r":
              try:
                  payload = self._get_bucket_md(bucket)
              except OFSFileNotFound:
                  # No MD found... create it
                  payload = {}
                  for l in self.list_labels(bucket):
                      payload[l] = {}
                      payload[l]['_label'] = l
                  if not self.quiet:
                      print("Had to create md file for %s" % bucket)
              except OFSException as e:
                  raise OFSException(e)
              if not label in payload:
                  payload[label] = {}
              payload[label].update(params)
              self.put_stream(bucket, MD_FILE, json.dumps(payload).encode('utf-8'), params={}, replace=True, add_md=False)
              return payload[label]
          else:
              raise OFSException("Cannot update MD in archive in 'r' mode"f update_metadata(self, bucket, label, params):
          '''Update the metadata with the provided dictionary of params.
  
          :param parmams: dictionary of key values (json serializable).
          '''
          if self.mode !="r":
              try:
                  payload = self._get_bucket_md(bucket)
              except OFSFileNotFound:
                  # No MD found... create it
                  payload = {}
                  for l in self.list_labels(bucket):
                      payload[l] = {}
                      payload[l]['_label'] = l
                  if not self.quiet:
                      print("Had to create md file for %s" % bucket)
              except OFSException as e:
                  raise OFSException(e)
              if not label in payload:
                  payload[label] = {}
              payload[label].update(params)
              self.put_stream(bucket, MD_FILE, json.dumps(payload).encode('utf-8'), params={}, replace=True, add_md=False)
              return payload[label]
          else:
              raise OFSException("Cannot update MD in archive in 'r' mode")
docs: Update the metadata with the provided dictionary of params.
  
          :param parmams: dictionary of key values (json serializable).