code: def scatter(cls, comm, in_array, out_array, root=0, stream=None):
      # in_array is a list of sparse matrices
      if comm.rank == root:
          nccl.groupStart()
          for peer, s_a in enumerate(in_array):
              if peer != root:
                  cls.send(comm, s_a, peer, stream)
          nccl.groupEnd()
          cls._assign_arrays(
              out_array,
              cls._get_internal_arrays(in_array[root]),
              in_array[root].shape,
          )
      else:
          cls.recv(comm, out_array, root, stream)
  
imports: import numpy
  import warnings
  import cupy
  from cupy.cuda import nccl
  from cupyx.distributed import _store
  from cupyx.distributed._comm import _Backend
  from cupyx.scipy import sparse
label_desc: Use image node_id 15 for calling the _SparseNCCLCommunicator obj's underlying member method code with example usage: obj.scatter(cls, comm, in_array, out_array, root, stream) without return types