docstr: ...Test is_zero method of HawkesKernel
code: def test_is_zero(self):
      """...Test is_zero method of HawkesKernel"""
      self.assertFalse(self.hawkes_kernel_exp.is_zero())
  
file_path: tick/tick/hawkes/simulation/tests/hawkes_kernel_test.py
imports: import unittest
  import numpy
  from tick.hawkes import HawkesKernelExp, HawkesKernelPowerLaw
label_desc: Use image node_id 2 for calling the Test obj's underlying member method code with example usage: obj.test_is_zero() without return types