* refactoring push loop for Collection on AST serialization
* refactoring push loop for Collection on AST serialization

neonichu/drafter,hendrikmaus/drafter,apiaryio/drafter,apiaryio/drafter,hendrikmaus/drafter,neonichu/drafter,apiaryio/drafter,apiaryio/drafter,hendrikmaus/drafter,apiaryio/drafter,neonichu/drafter,neonichu/drafter,hendrikmaus/drafter