code: def B2A_single_bit(xB):
      """Converts a single-bit BinarySharedTensor xB into an
          ArithmeticSharedTensor. This is done by:
  
      1. Generate ArithmeticSharedTensor [rA] and BinarySharedTensor =rB= with
          a common 1-bit value r.
      2. Hide xB with rB and open xB ^ rB
      3. If xB ^ rB = 0, then return [rA], otherwise return 1 - [rA]
          Note: This is an arithmetic xor of a single bit.
      """
      if comm.get().get_world_size() < 2:
          from .arithmetic import ArithmeticSharedTensor
  
          return ArithmeticSharedTensor(xB._tensor, precision=0, src=0)
  
      provider = mpc.get_default_provider()
      rA, rB = provider.B2A_rng(xB.size(), device=xB.device)
  
      z = (xB ^ rB).reveal()
      rA = rA * (1 - 2 * z) + z
      return rA
  
imports: import torch
  import fate.arch.protocol.mpc.communicator
  from fate.arch.protocol import mpc
  from fate.arch.protocol.mpc.common.util import count_wraps
  from fate.arch.protocol.mpc.config import cfg
label_desc: Use image node_id 12 for calling a global function with example usage: B2A_single_bit(xB) and returns: rA, ArithmeticSharedTensor