code: def test_show_columns_with_schema(self):
      inspector = mock.MagicMock()
      inspector.engine.dialect.identifier_preparer.quote_identifier = (
          lambda x: f'"{x}"'
      )
      inspector.bind.execute.return_value.fetchall = mock.MagicMock(
          return_value=["a", "b"]
      )
      table_name = "table_name"
      schema = "schema"
      result = PrestoEngineSpec._show_columns(
          inspector, table_name, schema
      )
      assert result == ["a", "b"]
      inspector.bind.execute.assert_called_once_with(
          f'SHOW COLUMNS FROM "{schema}"."{table_name}"'
      )
  
imports: from collections import namedtuple
  from textwrap import dedent
  from unittest import mock, skipUnless
  import pandas
  from flask.ctx import AppContext
  from sqlalchemy import types
  from sqlalchemy.sql import select
  from superset.db_engine_specs.presto import PrestoEngineSpec
  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
label_desc: Use image node_id 26 for calling the TestPrestoDbEngineSpec obj's underlying member method code with example usage: obj.test_show_columns_with_schema() without return types