code: def Erlang(k, lamda, tag=None):
      
      assert int(k) == k and k > 0, 'Erlang "k" must be a positive integer'
      assert lamda > 0, 'Erlang "lamda" must be greater than zero'
      return Gamma(k, lamda, tag)
docs: An Erlang random variate.
      
      This distribution is the same as a Gamma(k, theta) distribution, but 
      with the restriction that k must be a positive integer. This
      is provided for greater compatibility with other simulation tools, but
      provides no advantage over the Gamma distribution in its applications.
      
      Parameters
      ----------
      k : int
          The shape parameter (must be a positive integer)
      lamda : scalar
          The scale parameter (must be greater than zero)