code: public static boolean isLeaf(GraphQLType type) {
          GraphQLUnmodifiedType unmodifiedType = unwrapAll(type);
          return
                  unmodifiedType instanceof GraphQLScalarType
                          || unmodifiedType instanceof GraphQLEnumType;
      }
docs: Returns true if the given type is a leaf type, that it cant contain any more fields
  
  @param type the type to check
  
  @return true if the given type is a leaf type