code: function(destId, pos, options) {
                  corbel.validate.value('destId', destId);
                  var positionStartId = destId.indexOf('/');
                  if (positionStartId !== -1) {
                      destId = destId.substring(positionStartId + 1);
                  }
  
                  options = this.getDefaultOptions(options);
  
                  var args = corbel.utils.extend(options, {
                      url: this.buildUri(this.type, this.srcId, this.destType, destId),
                      contentType: 'application/json',
                      data: {
                          '_order': '$pos(' + pos + ')'
                      },
                      method: corbel.request.method.PUT
                  });
  
                  return this.request(args);
              }
docs: Move a relation
  @method
  @memberOf Resources.Relation
  @param  {Integer} pos          The new position
  @return {Promise}              ES6 promise that resolves to undefined (void) or rejects with a {@link CorbelError}