code: function (to, callback, param) {
              _gpfObjectForEach(this._members, function (attributeArray, member) {
                  member = _gpfDecodeAttributeMember(member);
                  attributeArray._array.forEach(function (attribute) {
                      if (!callback || callback(member, attribute, param)) {
                          to.add(member, attribute);
                      }
                  });
              });
              return to;
          }
docs: Copy the content of this map to a new one
  
  @param {gpf.attributes.Map} to recipient of the copy
  @param {Function} [callback=undefined] callback function to test if the mapping should be added
  @param {*} [param=undefined] param additional parameter for the callback
  @return {gpf.attributes.Map} to