code: def test_empty_fermi_sentence():
      """Test that an empty FermiSentence (fermi null operator) is
      converted to an empty PauliSentence or the null operator"""
      op = FermiSentence({})
  
      ps_op = jordan_wigner(op, ps=True)
      ps_op.simplify()
      assert ps_op == PauliSentence({})
  
      op = jordan_wigner(op).simplify()
      assert isinstance(op, SProd)
      assert isinstance(op.base, Identity)
      assert op.scalar == 0
  
imports: import pytest
  import pennylane
  from pennylane.ops import SProd, Identity
  from pennylane.pauli.conversion import pauli_sentence
  from pennylane.fermi.conversion import jordan_wigner
  from pennylane.pauli import PauliWord, PauliSentence
  from pennylane.fermi.fermionic import FermiWord, FermiSentence
label_desc: Use image node_id 6 for calling a global function with example usage: test_empty_fermi_sentence() without return types