code: def test_reduce():
      c = Constant(OrderedDict(x=Bint[3], y=Bint[2]), Number(1))
      assert c.reduce(ops.add, {"x", "y"}) is Number(6)
  
file_path: funsor/test/test_constant.py
imports: from collections import OrderedDict
  import funsor.ops
  from funsor.constant import Constant
  from funsor.delta import Delta
  from funsor.domains import Bint, Real
  from funsor.tensor import Tensor
  from funsor.terms import Number, Variable, to_data, to_funsor
  from funsor.testing import assert_close, randn, requires_backend
label_desc: Use image node_id 4 for calling a global function with example usage: test_reduce() without return types