code: def bits_in(length, keyspace):
      
      keyspace = len(keyspace)
      length_per_cycle = 64
      if length > length_per_cycle:
          bits = 0
          length_processed = 0
          cycles = ceil(length / length_per_cycle)
          for _ in range(int(cycles)):
              if length_processed + length_per_cycle > length:
                  length_per_cycle = length - length_processed
              bits += calc_bits_in(length_per_cycle, keyspace)
              length_processed += length_per_cycle
      else:
          bits = calc_bits_in(length, keyspace)
      return float(abs(bits))
docs: |log2(keyspace^length) = bits|
          -> (#float) number of bits of entropy in @length of characters for
              a given a @keyspace