* Support sequential run for standalone executor

* Add UTs

* Fix test_standalone_multiply_write

* Remove unnecessary UTs

* use yapf to format all python file

* yapf exclude two unittests file for they rely on writing and reading file, and format will break them

* disable diff_py_file because too many diff files cause command following failed

* add scope as membership

* functions complete

* fix bugs: garbage collectior

* deal unknow variable holder

* add

* 1. add unittest for operator_base

* code format