code: def is_pauli_word(observable):
      """
      Checks if an observable instance consists only of Pauli and Identity Operators.
  
      A Pauli word can be either:
  
      * A single pauli operator (see :class:`~.PauliX` for an example).
  
      * A :class:`.Tensor` instance containing Pauli operators.
  
      * A :class:`.Prod` instance containing Pauli operators.
  
      * A :class:`.SProd` instance containing a valid Pauli word.
  
      * A :class:`.Hamiltonian` instance with only one term.
  
      .. Warning::
  
          This function will only confirm that all operators are Pauli or Identity operators,
          and not whether the Observable is mathematically a Pauli word.
          If an Observable consists of multiple Pauli operators targeting the same wire, the
          function will return ``True`` regardless of any complex coefficients.
  
  
      Args:
          observable (~.Operator): the operator to be examined
  
      Returns:
          bool: true if the input observable is a Pauli word, false otherwise.
  
      **Example**
  
      >>> is_pauli_word(qml.Identity(0))
      True
      >>> is_pauli_word(qml.PauliX(0) @ qml.PauliZ(2))
      True
      >>> is_pauli_word(qml.PauliZ(0) @ qml.Hadamard(1))
      False
      >>> is_pauli_word(4 * qml.PauliX(0) @ qml.PauliZ(0))
      True
      """
      return _is_pauli_word(observable)
  
imports: from functools import lru_cache, reduce, singledispatch
  from itertools import product
  from typing import List, Union
  from warnings import warn
  import numpy
  import pennylane
  from pennylane.operation import Tensor
  from pennylane.ops import Hamiltonian, Identity, PauliX, PauliY, PauliZ, Prod, SProd
  from pennylane.tape import OperationRecorder
  from pennylane.wires import Wires
label_desc: Use image node_id 2 for calling a global function with example usage: is_pauli_word(observable) and returns: _is_pauli_word