code: def test_op_bool():
      N = (64,)
      domain = Domain(N, dx=[1.0] * len(N))
      params = jnp.ones(domain.N + (1,))
      field = OnGrid(params, domain)
      field_post = bool(field)
  
      assert jnp.allclose(field_post, field.on_grid != 0.0)
  
imports: import pytest
  from jax import jit
  from jax import numpy
  from jax import random
  from jaxdf.discretization import FiniteDifferences, FourierSeries, OnGrid
  from jaxdf.geometry import Domain
  from jaxdf.operators import inverse
label_desc: Use image node_id 8 for calling a global function with example usage: test_op_bool() without return types