code: def store(node)
           if !node.nil?
              @children.push(node) if !@children.include?(Node)
              node.parent = self if node.parent != self
           end
           node
        end
docs: This is the constructor for the ContainerNode class.
  
   ==== Parameters
   parent::     A reference to the parent node that owners the new
                ContainerNode object.
   This method adds a new node element to the end of the list of nodes
   maintained by a ContainerNode object. Nil objects are ignored.
  
   ==== Parameters
   node::  A reference to the Node object to be added.