class_docstr: Test ability to marshall select slider protos.
docstr: Test that format_func sends down correct strings of the options.
docstr_tok: ["Test","that","format_func","sends","down","correct","strings","of","the","options","."]
code: def test_format_func(self):
      """Test that format_func sends down correct strings of the options."""
      DAYS_OF_WEEK = [
          "Sunday",
          "Monday",
          "Tuesday",
          "Wednesday",
          "Thursday",
          "Friday",
          "Saturday",
      ]
      st.select_slider(
          "the label",
          value=1,
          options=[0, 1, 2, 3, 4, 5, 6],
          format_func=lambda x: DAYS_OF_WEEK[x],
      )
  
      c = self.get_delta_from_queue().new_element.slider
      self.assertEqual(c.default, [1])
      self.assertEqual(c.options, DAYS_OF_WEEK)
  
imports: from unittest.mock import MagicMock, patch
  import numpy
  import pandas
  import pytest
  from parameterized import parameterized
  import streamlit
  from streamlit.errors import StreamlitAPIException
  from streamlit.proto.LabelVisibilityMessage_pb2 import LabelVisibilityMessage
  from streamlit.testing.v1.app_test import AppTest
  from streamlit.testing.v1.util import patch_config_options
  from tests.delta_generator_test_case import DeltaGeneratorTestCase
label_desc: Use image node_id 10 for calling the SliderTest obj's underlying member method code with example usage: obj.test_format_func() without return types