Map<String, ManagedAttributeDescription> attributes

Source 

Map<String, ManagedAttributeDescription> get attributes => _attributes;
void attributes=(Map<String, ManagedAttributeDescription> m)

Source 

set attributes(Map<String, ManagedAttributeDescription> m) {
  _attributes = m;
  _primaryKey = m.values
      .firstWhere((attrDesc) => attrDesc.isPrimaryKey, orElse: () => null)
      ?.name;
}