code: public List<GraphQLObjectType> getImplementations(GraphQLInterfaceType type) {
          List<GraphQLObjectType> implementations = byInterface.get(type.getName());
          return (implementations == null)
                  ? Collections.emptyList()
                  : Collections.unmodifiableList(sortGraphQLTypes(implementations));
      }
docs: This will return the list of {@link graphql.schema.GraphQLObjectType} types that implement the given
  interface type.
  
  @param type interface type to obtain implementations of.
  
  @return list of types implementing provided interface