def __init__(self, var_id, parent=None):
    self.var_id = var_id
    self.set_parent(parent)
    self.children = []
    self.tree = None
def __init__(self, var_id, parent=None):
    self.var_id = var_id
    self.set_parent(parent)
    self.children = []
    self.tree = None