code: def test_widget_eventual_data_with_server(self):
      # should fail
      widget = PerspectiveWidget(None, server=True)
  
      with raises(PerspectiveError):
          widget._make_load_message()
  
      # then succeed
      widget.load(Table({"a": np.arange(0, 50)}))
      load_msg = widget._make_load_message()
      assert load_msg.to_dict() == {
          "id": -2,
          "type": "table",
          "data": {"table_name": widget.table_name},
      }
  
imports: from datetime import date, datetime
  from functools import partial
  from types import MethodType
  import numpy
  from perspective import PerspectiveError, PerspectiveWidget, Table
  from pytest import raises
label_desc: Use image node_id 21 for calling the TestWidget obj's underlying member method code with example usage: obj.test_widget_eventual_data_with_server() without return types