code: def test_functional_ongrid():
      x = OnGrid(jnp.asarray([1.0]), domain)
      y = jnp.sum(x.on_grid)
      z = operators.functions.functional(x)(jnp.sum)
      assert np.allclose(z, y)
  
file_path: jaxdf/tests/test_functions.py
imports: import jax
  import numpy
  from jax import jit
  from jax import numpy
  from jaxdf import *
label_desc: Use image node_id 7 for calling a global function with example usage: test_functional_ongrid() without return types