stack.py now passes unittests. added missing parentheses in conditional in method __precedence()
stack.py now passes unittests. added missing parentheses in conditional in method __precedence()

Signed-off-by: IanDoarn <f713c9db13db6a4329f541ca383ec459bfaa5ce8@zimmerbiomet.com>

OmkarPathak/pygorithm