[oracle] How to see PL/SQL Stored Function body in Oracle

I have a stored function in Oracle database pAdCampaign.fGetAlgoGroupKey. How to see the code of this function.?

You can also use DBMS_METADATA:

select dbms_metadata.get_ddl('FUNCTION', 'FGETALGOGROUPKEY', 'PADCAMPAIGN') 
from dual

SELECT text 
FROM all_source
where name = 'FGETALGOGROUPKEY'
order by line

alternatively:

select dbms_metadata.get_ddl('FUNCTION', 'FGETALGOGROUPKEY')
from dual;