code: def test_is_cation_pi(self):
      cation_position = np.array([[2.0, 0.0, 0.0]])
      ring_center_true = np.array([4.0, 0.0, 0.0])
      ring_center_false = np.array([10.0, 0.0, 0.0])
      ring_normal_true = np.array([1.0, 0.0, 0.0])
      ring_normal_false = np.array([0.0, 1.0, 0.0])
  
      # parallel normals
      self.assertTrue(
          is_cation_pi(
              cation_position, ring_center_true, ring_normal_true
          )
      )
      # perpendicular normals
      self.assertFalse(
          is_cation_pi(
              cation_position, ring_center_true, ring_normal_false
          )
      )
      # too far away
      self.assertFalse(
          is_cation_pi(
              cation_position, ring_center_false, ring_normal_true
          )
      )
  
imports: import os
  import unittest
  import numpy
  from deepchem.utils.rdkit_utils import load_molecule
  from deepchem.utils.rdkit_utils import compute_ring_center
  from deepchem.utils.rdkit_utils import compute_ring_normal
  from deepchem.utils.noncovalent_utils import is_pi_parallel
  from deepchem.utils.noncovalent_utils import is_pi_t
  from deepchem.utils.noncovalent_utils import compute_pi_stack
  from deepchem.utils.noncovalent_utils import is_cation_pi
  from deepchem.utils.noncovalent_utils import compute_cation_pi
  from deepchem.utils.noncovalent_utils import compute_binding_pocket_cation_pi
label_desc: Use image node_id 7 for calling the TestPiInteractions obj's underlying member method code with example usage: obj.test_is_cation_pi() without return types