class_docstr: Hawkes kernel with exponential decay
  
  .. math::
      \phi(t) = \alpha \beta \exp (- \beta t) 1_{t > 0}
  
  where :math:`\alpha` is the intensity of the kernel and
  :math:`\beta` its decay.
  
  Parameters
  ----------
  intensity : `float`
      Intensity of the kernel, also noted :math:`\alpha`
  
  decay : `float`
      Decay of the kernel, also noted :math:`\beta`
code: def __repr__(self):
      return self.__str__().replace(" ", "")
  
file_path: tick/tick/hawkes/simulation/hawkes_kernels/hawkes_kernel_exp.py
imports: from tick.hawkes.simulation.build.hawkes_simulation import HawkesKernelExp
  from .hawkes_kernel import HawkesKernel
label_desc: Use image node_id 5 for calling the HawkesKernelExp obj's underlying member method code with example usage: obj.__repr__() and returns: self