code: def test_populate_dict_unmapped(self):
      uowcommit, a1, b1, a_mapper, b_mapper = self._fixture()
      a1.obj().id = 10
      pairs = [(b_mapper.c.id, b_mapper.c.id)]
      dest = {}
      assert_raises_message(
          orm_exc.UnmappedColumnError,
          "Can't execute sync rule for source column 't2.id'; "
          r"mapper 'Mapper\[A\(t1\)\]' does not map this column.",
          sync.populate_dict,
          a1,
          a_mapper,
          dest,
          pairs,
      )
  
imports: from sqlalchemy import ForeignKey
  from sqlalchemy import Integer
  from sqlalchemy import testing
  from sqlalchemy.orm import attributes
  from sqlalchemy.orm import class_mapper
  from sqlalchemy.orm import exc
  from sqlalchemy.orm import sync
  from sqlalchemy.orm import unitofwork
  from sqlalchemy.testing import assert_raises_message
  from sqlalchemy.testing import eq_
  from sqlalchemy.testing import fixtures
  from sqlalchemy.testing.fixtures import fixture_session
  from sqlalchemy.testing.schema import Column
  from sqlalchemy.testing.schema import Table
label_desc: Use image node_id 15 for calling the SyncTest obj's underlying member method code with example usage: obj.test_populate_dict_unmapped() without return types