code: public GraphQLObjectType getObjectType(String typeName) {
          GraphQLType graphQLType = typeMap.get(typeName);
          if (graphQLType != null) {
              assertTrue(graphQLType instanceof GraphQLObjectType,
                      format("You have asked for named object type '%s' but its not an object type but rather a '%s'", typeName, graphQLType.getClass().getName()));
          }
          return (GraphQLObjectType) graphQLType;
      }
docs: Called to return a named {@link graphql.schema.GraphQLObjectType} from the schema
  
  @param typeName the name of the type
  
  @return a graphql object type or null if there is one
  
  @throws graphql.GraphQLException if the type is NOT a object type