class Node(object):
    def __init__(self, children=None):
        self.children = children

class StatementNode(Node):
    def __init__(self, children=None):
        Node.__init__(self, children)

class ExprNode(Node):
    def __init__(self, children=None):
        Node.__init__(self, children)

class CExprNode(ExprNode):
    def __init__(self, cstring):
        ExprNode.__init__(self)
        self.cstring = cstring