code: def id(self, sort_ops=True):
          
          if len(self._ops) == 0 and not sort_ops:
              # This is nefariously backwards-compatibility breaking. There's potentially
              # lots of code floating around that says is_identity = term.id() == ''
              # Please use `is_identity(term)`!
              # Therefore, we only return 'I' when sort_ops is set to False, which is the newer
              # way of calling this function and implies the user knows what they're doing.
              return 'I'
  
          if sort_ops and len(self._ops) > 1:
              warnings.warn("`PauliTerm.id()` will not work on PauliTerms where the qubits are not "
                            "sortable and should be avoided in favor of `operations_as_set`.",
                            FutureWarning)
              return ''.join("{}{}".format(self._ops[q], q) for q in sorted(self._ops.keys()))
          else:
              return ''.join("{}{}".format(p, q) for q, p in self._ops.items())
docs: Returns an identifier string for the PauliTerm (ignoring the coefficient).
  
          Don't use this to compare terms. This function will not work with qubits that
          aren't sortable.
  
          :param sort_ops: Whether to sort operations by qubit. This is True by default for
              backwards compatibility but will change in a future version. Callers should never rely
              on comparing id's for testing equality. See ``operations_as_set`` instead.
          :return: A string representation of this term's operations.
          :rtype: string