def _sample_qubit_pauli_maps():
    """All combinations of having a Pauli or nothing on 3 qubits.
    Yields 64 qubit pauli maps
    """
    qubits = _make_qubits(3)
    paulis_or_none = (None, cirq.X, cirq.Y, cirq.Z)
    for paulis in itertools.product(paulis_or_none, repeat=len(qubits)):
        yield {qubit: pauli for qubit, pauli in zip(qubits, paulis) if pauli is not None}
All combinations of having a Pauli or nothing on 3 qubits.
    Yields 64 qubit pauli maps
    
cirq-core/cirq/ops/pauli_string_test.py