docstr: Simulate realization in which some nodes are sometimes empty
          
docstr_tok: ["Simulate","realization","in","which","some","nodes","are","sometimes","empty"]
code: def simulate_sparse_realization(self):
      """Simulate realization in which some nodes are sometimes empty"""
      baseline = np.array([0.3, 0.001])
      adjacency = np.array(
          [[[0.5, 0.3], [0.8, 0.2]], [[0.0, 0.0], [1.3, 0.9]]]
      )
  
      sim = SimuHawkesSumExpKernels(
          adjacency=adjacency,
          decays=self.decays,
          baseline=baseline,
          verbose=False,
          seed=13487,
          end_time=500,
      )
      sim.adjust_spectral_radius(0.8)
      multi = SimuHawkesMulti(sim, n_simulations=100)
  
      adjacency = sim.adjacency
      multi.simulate()
  
      # Check that some but not all realizations are empty
      self.assertGreater(
          max(map(lambda r: len(r[1]), multi.timestamps)), 1
      )
      self.assertEqual(
          min(map(lambda r: len(r[1]), multi.timestamps)), 0
      )
  
      return baseline, adjacency, multi.timestamps
  
imports: import unittest
  import numpy
  from tick.base.inference import InferenceTest
  from tick.hawkes import SimuHawkesSumExpKernels, SimuHawkesMulti
  from tick.hawkes.inference import HawkesSumExpKern
  from tick.prox import ProxNuclear
  from tick.prox import ProxPositive, ProxL1, ProxL2Sq, ProxElasticNet
  from tick.solver import AGD, GD, BFGS, SGD, SVRG
label_desc: Use image node_id 3 for calling the Test obj's underlying member method code with example usage: obj.simulate_sparse_realization() and returns: baseline,  adjacency,  multi