Create the PTF implementation package noop_p.

CREATE PACKAGE noop_p AS 
   FUNCTION describe(tab IN OUT DBMS_TF.table_t) 
		          RETURN DBMS_TF.describe_t; 
   PROCEDURE noop_fetch; 
END noop_p; 

To provide a method name override, you can specify the new method names using DBMS_TF.Method_Names collection.

CREATE PACKAGE BODY noop_p AS 
  FUNCTION describe(tab IN OUT DBMS_TF.table_t) 
		         RETURN DBMS_TF.describe_t AS 
	methods DBMS_TF.methods_t := DBMS_TF.methods_t(DBMS_TF.fetch_rows => 'Noop_Fetch'); 
     BEGIN 
	  RETURN DBMS_TF.describe_t(method_names => methods); 
     END; 
     PROCEDURE noop_fetch AS  
     BEGIN  
	  RETURN;  
     END; 
END noop_p; 

The noop PTF is defined to execute the noop_p when it is invoked.

CREATE FUNCTION noop (t TABLE)  
  RETURN TABLE PIPELINED ROW POLYMORPHIC USING noop_p; 

The PTF is invoked in the FROM clause of a query block.

SELECT *  
FROM noop(scott.emp) 
WHERE deptno =10