find language of this pda code example

Example: finding the language of a PDA

(q0, a, z) (q0, az)        
(q0, a, a) (q0, aa)     
(q0, b, a) (q1, a)  [ Indicates no operation only state change ]
(q1, b, a) (q2, a)  [ Indicates no operation only state change ]
(q2, b, a) (q3,  )  [Indicates pop operation ]
(q3, b, a) (q2, a )  [ Indicates no operation only state change ]
(q3, , z) (qf, z )