code: def nonzero_abstract(x):
      n = x.dim()
      ctx = torch.library.get_ctx()
      nnz = ctx.create_unbacked_symint()
      shape = [nnz, n]
      return x.new_empty(shape, dtype=torch.long)
  
label_desc: Use image node_id 1 for calling a global function with example usage: nonzero_abstract(x) and returns: x