code: def unary_operate(lhs, op, block_indexes):
      block_index_set = set(block_indexes)
      op_ret = lhs.mapValues(
          lambda blocks: [
              op(blocks[bid]) if bid in block_index_set else blocks[bid]
              for bid in range(len(blocks))
          ]
      )
  
      return op_ret
  
label_desc: Use image node_id 2 for calling a global function with example usage: unary_operate(lhs, op, block_indexes) and returns: op_ret