code: function (data, key, schemaType, schemaDefinition) {
  
                  if (schemaDefinition && schemaDefinition.key) {
                      key = schemaDefinition.key;
                  }
  
                  return data[key];
              }
docs: This method can be used to map payload values to the correct schema key
  For example to map "company_id" to "company" : {id: "2"} ...
  
  @param {Object} data The payload data
  @param {String} key The schema key
  @param {Function} schemaType The schema typ
  @param {Object} schemaDefinition
  @return {*} Returns the correct value for a reference and schemaType
  @private