Node - #empty#

• For Xmind ChatTree, the first line of node content must be "#empty#", and then there is no need for other lines of content, such as:

  #empty#

• For Python ChatTree, the first parameter of chattree.create_node() must be "#empty#", and the second parameter dict is empty, such as:

  xxx_node = chattree.create_node("#empty#", {})

• The node itself does not perform any operations. It is mainly used to aggregate/group subsequent nodes in the topology. It is needed to express some special topology logic.