code: def test_drop_seq_checkfirst(self):
      m, t1, t2, s1, s2 = self._table_seq_fixture()
      generator = self._mock_drop_fixture(
          True, [t1, t2], item_exists=lambda t: t in ("t1", "s1")
      )
  
      self._assert_drop([t1, s1], generator, m)
  
imports: from unittest.mock import Mock
  from sqlalchemy import Column
  from sqlalchemy import ForeignKey
  from sqlalchemy import Index
  from sqlalchemy import Integer
  from sqlalchemy import MetaData
  from sqlalchemy import schema
  from sqlalchemy import Sequence
  from sqlalchemy import Table
  from sqlalchemy.sql.ddl import SchemaDropper
  from sqlalchemy.sql.ddl import SchemaGenerator
  from sqlalchemy.testing import fixtures
label_desc: Use image node_id 12 for calling the EmitDDLTest obj's underlying member method code with example usage: obj.test_drop_seq_checkfirst() without return types