SUB function is called instead of SQRT

[palatinb]

Short description	SUB function is called instead of SQRT
Expected operation	SQRT function should be called when we call the SQRT operator
Experienced operation	SUB function is called
Reproductive steps	After running the SQRT operation it can be reproduced the error
Error location	test-automation-engineer-python-junior/icalc.py Line 35 in 865c772 print(self.cal.sub(*parse(arg)))
Test result	Not OK
Priority	High