docs: protected SDLDefinition createTypeSystemDefinition(GraphqlParser.TypeSystemDefinitionContext ctx) {
          if (ctx.schemaDefinition() != null) {
              return createSchemaDefinition(ctx.schemaDefinition());
          } else if (ctx.directiveDefinition() != null) {
              return createDirectiveDefinition(ctx.directiveDefinition());
          } else if (ctx.typeDefinition() != null) {
              return createTypeDefinition(ctx.typeDefinition());
          } else if (ctx.typeExtension() != null) {
              return createTypeExtension(ctx.typeExtension());
          } else {
              return assertShouldNeverHappen();
          }
      }