size_t nrRelations() const {return childs_.size();}
bool Node::IsParentOf(const Node *node)
{
return (std::find(childs_.begin(), childs_.end(), node) != childs_.end());
}
void addRelation(Ptr_ el){childs_.push_back(el);}
Node* Node::AddChild(Node* node)
{
childs_.push_back(node);
return node;
}