docs: function _mainMap(data, schema, options) {
      options = options || {};
      var mapping = _map(data, schema, options);
      if (options.removeChanged) {
          var mappedFields = _getMappedFields(schema);
          mappedFields.forEach(function (field) {
              _removeMappedFields(mapping, field);
          });
          mapping = _cleanArrays(mapping);
      }
      return mapping;
  }