code: def _pw_prefactor_tensor(observable: Tensor):
      if is_pauli_word(observable):
          return list(pauli_sentence(observable).values())[
              0
          ]  # only one term,
      raise ValueError(f"Expected a valid Pauli word, got {observable}")
  
file_path: pennylane/pennylane/pauli/pauli_interface.py
imports: from typing import Union
  from functools import singledispatch
  from pennylane.ops import Hamiltonian, Identity, PauliX, PauliY, PauliZ, Prod, SProd
  from pennylane.operation import Tensor
  from .utils import is_pauli_word
  from .conversion import pauli_sentence
label_desc: Use image node_id 4 for calling a global function with example usage: _pw_prefactor_tensor(observable) and returns: list