code: function(fields, fieldName, displayName) {
                  var newField = {};
                  newField[fieldName] = {
                      displayName: displayName
                  };
                  _.extend(fields, newField);
              }
docs: For internal use only. Adds the given field to the given
  collection of fields.
  @param fields {object} object of existing fields
  @param fieldName {string} name of the field for the server API
  @param displayName {string} name of the field to display to the
  user