How to do the square root of X operation in Qiskit

Question

I'm trying to do the Bell Inequality Test in Qiskit but to do that you need preform the controlled negative square root of X operation. An example of this in Cirq is

cirq.CNOT(bob_ref, bob)**-0.5

I tried to do something similar in Qiskit and it gave me an error

cir.cx(bob_ref, bob)**-0.5