code: def test_basic(object) -> None:
      val = bt.cumsum("foo")
      assert isinstance(val, Expr)
      assert isinstance(val.expr, CumSum)
      assert val.expr.field == "foo"
      assert val.expr.include_zero is False
  
imports: from __future__ import annotations
  import pytest
  from bokeh.core.property.vectorization import Expr, Field
  from bokeh.models import CategoricalColorMapper, CategoricalMarkerMapper, CategoricalPatternMapper, CumSum, Dodge, EqHistColorMapper, FactorRange, Jitter, LinearColorMapper, LogColorMapper, Stack
  from tests.support.util.api import verify_all
  import bokeh.transform
label_desc: Use image node_id 1 for calling the Test_cumsum obj's underlying member method code with example usage: obj.test_basic(object) without return types