code: def __getitem__(self, n):
      return (MPZ_ONE << (n - 1)) - 1
  
imports: import math
  from bisect import bisect
  import sys
  from .backend import MPZ, MPZ_TYPE, MPZ_ZERO, MPZ_ONE, MPZ_TWO, MPZ_FIVE, BACKEND, STRICT, HASH_MODULUS, HASH_BITS, gmpy, sage, sage_utils
  from .libintmath import giant_steps, trailtable, bctable, lshift, rshift, bitcount, trailing, sqrt_fixed, numeral, isqrt, isqrt_fast, sqrtrem, bin_to_radix
label_desc: Use image node_id 1 for calling the h_mask_big obj's underlying member method code with example usage: obj.__getitem__(n) and returns: unknown