code: def Exponential(lamda, tag=None):
      
      assert lamda > 0, 'Exponential "lamda" must be greater than zero'
      return uv(ss.expon(scale=1.0 / lamda), tag=tag)
docs: An Exponential random variate
      
      Parameters
      ----------
      lamda : scalar
          The inverse scale (as shown on Wikipedia). (FYI: mu = 1/lamda.)