def test_normal_ordered():
    'Test normal_ordered function'
    op = FermionOperator('3 4^')
    assert (str(normal_ordered(op)) == '-1 [4^ 3] ')
Test normal_ordered function
def test_normal_ordered():
    
    op = FermionOperator('3 4^')
    assert (str(normal_ordered(op)) == '-1 [4^ 3] ')