code: def exponential_kernel(t, intensity, decay):
      return intensity * decay * np.exp(-decay * t)
  
file_path: tick/tick/hawkes/model/tests/model_hawkes_test_utils.py
imports: import numpy
  from scipy.integrate import quad
label_desc: Use image node_id 1 for calling a global function with example usage: exponential_kernel(t, intensity, decay) and returns: unknown