Gswap cannot be used as a two-qubit standard native gate for two-qubit RB as CliffordCompilationRules taking too long

[vsandinh]

Describe the bug
I tried to run RB-Overview.ipynb file but with small change in the native gate set.
I used 'Gswap' which is one of the standard two-qubit gates in the documentation of QubitProcessorSpec class. However, it is taking forever to instantiate the CliffordCompilationRules class.

I also tried a custom two-qubit gate which is iSWAP, the program showed similar behavior

To Reproduce
Here is the code:

from __future__ import print_function #python 2 & 3 compatibility
import pygsti
from pygsti.processors import QubitProcessorSpec as QPS
from pygsti.processors import CliffordCompilationRules as CCR

n_qubits = 2
qubit_labels = ['Q0','Q1'] 
gate_names = ['Gxpi2', 'Gxmpi2', 'Gypi2', 'Gympi2', 'Gswap'] 
availability = {'Gswap':[('Q0','Q1')]}
pspec = QPS(n_qubits, gate_names, availability=availability,
            qubit_labels=qubit_labels, )

compilations = {'absolute': CCR.create_standard(pspec, 'absolute', ('paulis', '1Qcliffords'), verbosity=0),            
                'paulieq': CCR.create_standard(pspec, 'paulieq', ('1Qcliffords', 'allcnots'), verbosity=0)}

Expected behavior
CliffordCompilationRules should be instantiated.

Environment (please complete the following information):

• pyGSTi version 0.9.12.3
• python version 3.9.7
• OS OSX 14.5