docs: def remove_symbol_from_dist(dist, index):
      '''
      prob is a ndarray representing a probability distribution.
      index is a number between 0 and and the number of symbols ( len(prob)-1 )
      return the probability distribution if the element at 'index' was no longer available
      '''
      if type(dist) is not Distribution:
          raise TypeError("remove_symbol_from_dist got an object ot type {0}".format(type(dist)))
  
      new_prob = dist.prob.copy()
      new_prob[index]=0
      new_prob /= sum(new_prob)
      return Distribution(new_prob)