docstr: test that pending doesn't add an item that's not a net add.
docstr_tok: ["test","that","pending","does","n't","add","an","item","that","'s","not","a","net","add","."]
code: def test_add_remove_pending_backref(self):
      """test that pending doesn't add an item that's not a net add."""
  
      Item, Keyword = (self.classes.Item, self.classes.Keyword)
  
      session = fixture_session(autoflush=False, future=True)
  
      i1 = Item(description="i1")
      session.add(i1)
      session.commit()
  
      session.expire(i1, ["keywords"])
  
      k1 = Keyword(name="k1")
      k1.items.append(i1)
      k1.items.remove(i1)
      eq_(i1.keywords, [])
  
imports: from sqlalchemy import testing
  from sqlalchemy import text
  from sqlalchemy.orm import attributes
  from sqlalchemy.orm import backref
  from sqlalchemy.orm import relationship
  from sqlalchemy.orm import Session
  from sqlalchemy.testing import eq_
  from sqlalchemy.testing import is_
  from sqlalchemy.testing.fixtures import fixture_session
  from test.orm import _fixtures
label_desc: Use image node_id 2 for calling the M2MCollectionMoveTest obj's underlying member method code with example usage: obj.test_add_remove_pending_backref() without return types