* add ChangeInstrument to ops
Adding Change instrument OP. This op allows one to use features of a different instrument.
* Update __init__.py
update parse_field to accommodate ChangeInstrument
* Propose test
* Add test case and fix bug
* Update ops.py
* Update ops.py
* simplify the operator further
* implement abstract method
* fix arg bug
* clean test
Co-authored-by: Young <afe.young@gmail.com>
Co-authored-by: you-n-g <you-n-g@users.noreply.github.com>
