code: def test_add_fk(self):
      m1 = MetaData()
      m2 = MetaData()
  
      Table(
          "some_table",
          m1,
          Column("id", Integer, primary_key=True),
          Column("test", String(10)),
      )
  
      Table(
          "user",
          m1,
          Column("id", Integer, primary_key=True),
          Column("name", String(50), nullable=False),
          Column("a1", String(10), server_default="x"),
          Column("test2", String(10)),
      )
  
      Table(
          "some_table",
          m2,
          Column("id", Integer, primary_key=True),
          Column("test", String(10)),
      )
  
      Table(
          "user",
          m2,
          Column("id", Integer, primary_key=True),
          Column("name", String(50), nullable=False),
          Column("a1", String(10), server_default="x"),
          Column("test2", String(10)),
          ForeignKeyConstraint(["test2"], ["some_table.test"]),
      )
  
      diffs = self._fixture(m1, m2)
  
      self._assert_fk_diff(
          diffs[0], "add_fk", "user", ["test2"], "some_table", ["test"]
      )
  
imports: from sqlalchemy import Column
  from sqlalchemy import ForeignKeyConstraint
  from sqlalchemy import Integer
  from sqlalchemy import MetaData
  from sqlalchemy import String
  from sqlalchemy import Table
  from ._autogen_fixtures import AutogenFixtureTest
  from ...testing import combinations
  from ...testing import config
  from ...testing import eq_
  from ...testing import mock
  from ...testing import TestBase
label_desc: Use image node_id 2 for calling the AutogenerateForeignKeysTest obj's underlying member method code with example usage: obj.test_add_fk() without return types