code: def test_extract_limit_from_query(
      self, engine_spec_class=BaseEngineSpec
  ):
      q0 = "select * from table"
      q1 = "select * from mytable limit 10"
      q2 = "select * from (select * from my_subquery limit 10) where col=1 limit 20"
      q3 = "select * from (select * from my_subquery limit 10);"
      q4 = "select * from (select * from my_subquery limit 10) where col=1 limit 20;"
      q5 = "select * from mytable limit 20, 10"
      q6 = "select * from mytable limit 10 offset 20"
      q7 = "select * from mytable limit"
      q8 = "select * from mytable limit 10.0"
      q9 = "select * from mytable limit x"
      q10 = "select * from mytable limit 20, x"
      q11 = "select * from mytable limit x offset 20"
  
      self.assertEqual(engine_spec_class.get_limit_from_sql(q0), None)
      self.assertEqual(engine_spec_class.get_limit_from_sql(q1), 10)
      self.assertEqual(engine_spec_class.get_limit_from_sql(q2), 20)
      self.assertEqual(engine_spec_class.get_limit_from_sql(q3), None)
      self.assertEqual(engine_spec_class.get_limit_from_sql(q4), 20)
      self.assertEqual(engine_spec_class.get_limit_from_sql(q5), 10)
      self.assertEqual(engine_spec_class.get_limit_from_sql(q6), 10)
      self.assertEqual(engine_spec_class.get_limit_from_sql(q7), None)
      self.assertEqual(engine_spec_class.get_limit_from_sql(q8), None)
      self.assertEqual(engine_spec_class.get_limit_from_sql(q9), None)
      self.assertEqual(engine_spec_class.get_limit_from_sql(q10), None)
      self.assertEqual(engine_spec_class.get_limit_from_sql(q11), None)
  
imports: import datetime
  from unittest import mock
  import pytest
  from superset.connectors.sqla.models import TableColumn
  from superset.db_engine_specs import load_engine_specs
  from superset.db_engine_specs.base import BaseEngineSpec, BasicParametersMixin, builtin_time_grains, LimitMethod
  from superset.db_engine_specs.mysql import MySQLEngineSpec
  from superset.db_engine_specs.sqlite import SqliteEngineSpec
  from superset.errors import ErrorLevel, SupersetError, SupersetErrorType
  from superset.sql_parse import ParsedQuery
  from superset.utils.database import get_example_database
  from tests.integration_tests.db_engine_specs.base_tests import TestDbEngineSpec
  from tests.integration_tests.test_app import app
  from ..fixtures.birth_names_dashboard import load_birth_names_dashboard_with_slices, load_birth_names_data
  from ..fixtures.energy_dashboard import load_energy_table_data, load_energy_table_with_slice
  from ..fixtures.pyodbcRow import Row
label_desc: Use image node_id 1 for calling the TestDbEngineSpecs obj's underlying member method code with example usage: obj.test_extract_limit_from_query(engine_spec_class) without return types