code: public boolean functionAvailable(String methName)
    {
        Object tblEntry = m_functionID.get(methName);
        if (null != tblEntry) return true;
        else{
                tblEntry = m_functionID_customer.get(methName);
                return (null != tblEntry)? true : false;
        }
    }
docs: Tell if a built-in, non-namespaced function is available.
  
  @param methName The local name of the function.
  
  @return True if the function can be executed.