`stim.target_combiner` and `stim.PauliString` not supported for `OBSERVABLE_INCLUDE`

[oscarhiggott]

The new pauli targets for OBSERVABLE_INCLUDE only works with stim.target_pauli but not stim.target_combiner or stim.PauliString. Instead I would have expected stim.target_combiner or stim.PauliString to be supported and not stim.target_pauli alone since it is a pauli product being included into the observable.

For example:

import stim

circuit = stim.Circuit()

obs_pauli = stim.PauliString("IXYZIIXYZ")

# Works fine
circuit.append("MPP", targets=[obs_pauli])

# ValueError: Gate OBSERVABLE_INCLUDE only takes measurement record targets and Pauli targets (rec[-k], Xk, Yk, Zk).
circuit.append("OBSERVABLE_INCLUDE", targets=[obs_pauli], arg=0)
# ValueError: Gate OBSERVABLE_INCLUDE only takes measurement record targets and Pauli targets (rec[-k], Xk, Yk, Zk).
circuit.append(
    "OBSERVABLE_INCLUDE", targets=[*stim.target_combined_paulis(obs_pauli)], arg=1
)

obs_pauli_targets = []
for i in range(len(obs_pauli)):
    if obs_pauli[i] != 0:
        obs_pauli_targets.append(stim.target_pauli(i, obs_pauli[i]))
# Works fine
circuit.append("OBSERVABLE_INCLUDE", targets=obs_pauli_targets, arg=1)