code: def test_string_service(self):
      source = ogc.WMSRasterSource(self.URI, self.layer)
      from owslib.map.wms111 import WebMapService_1_1_1
      from owslib.map.wms130 import WebMapService_1_3_0
  
      assert isinstance(
          source.service, (WebMapService_1_1_1, WebMapService_1_3_0)
      )
      assert isinstance(source.layers, list)
      assert source.layers == [self.layer]
  
imports: from unittest import mock
  from xml.etree.ElementTree import ParseError
  import numpy
  import pytest
  import cartopy.crs
  from cartopy.tests.conftest import _HAS_PYKDTREE_OR_SCIPY
  import cartopy.io.ogc_clients
  from cartopy.io.ogc_clients import _OWSLIB_AVAILABLE
label_desc: Use image node_id 1 for calling the TestWMSRasterSource obj's underlying member method code with example usage: obj.test_string_service() without return types