code: def refill_random(self):
          ''' refill the list of random_umis '''
          self.random_umis = np.random.choice(
              list(self.umis.keys()), self.random_fill_size, p=self.prob)
          self.random_ix = f refill_random(self):
          ''' refill the list of random_umis '''
          self.random_umis = np.random.choice(
              list(self.umis.keys()), self.random_fill_size, p=self.prob)
          self.random_ix = 0
docs: refill the list of random_umis