code: def base10_integer_to_basek_string(k, x):
      
      if not (2 <= k <= max_k_labeled):
          raise ValueError("k must be in range [2, %d]: %s"
                           % (max_k_labeled, k))
      return ((x == 0) and numerals[0]) or \
          (base10_integer_to_basek_string(k, x // k).\
           lstrip(numerals[0]) + numerals[x % k])
docs: Convert an integer into a base k string.