code: def normalize_pdf(mu, pofmu):
      
      if min(pofmu) < 0:
          raise ValueError("Probabilities cannot be negative, don't ask me to "
                           "normalize a function with negative values!")
      if min(mu) < 0:
          raise ValueError("Rates cannot be negative, don't ask me to "
                           "normalize a function over a negative domain!")
  
      dp = integral_element(mu, pofmu)
      return mu, pofmu/sum(dp)
docs: Takes a function pofmu defined at rate sample values mu and
      normalizes it to be a suitable pdf. Both mu and pofmu must be
      arrays or lists of the same length.