code: function isSchemaOfCommonNames(schema: GraphQLSchema): boolean {
    const queryType = schema.getQueryType();
    if (queryType && queryType.name !== 'Query') {
      return false;
    }
  
    const mutationType = schema.getMutationType();
    if (mutationType && mutationType.name !== 'Mutation') {
      return false;
    }
  
    const subscriptionType = schema.getSubscriptionType();
    if (subscriptionType && subscriptionType.name !== 'Subscription') {
      return false;
    }
  
    return true;
  }
docs: GraphQL schema define root types for each type of operation. These types are
  the same as any other type and can be named in any manner, however there is
  a common naming convention:
  
  schema {
  query: Query
  mutation: Mutation
  }
  
  When using this naming convention, the schema description can be omitted.