code: def add_child(self, c):
      if isinstance(c, type(self)):
          c.parent = self
      self.children.append(c)
      self.num_children = self.num_children + 1
  
imports: from operator import itemgetter
  import numpy
label_desc: Use image node_id 3 for calling the Tree obj's underlying member method code with example usage: obj.add_child(c) without return types