def get_param_default_value(node):
    """
    Precondition : node is a parameter of a function/method
    returns the default value if present or None
    Defined at the rhs of an = sign.
    """
    # print([x.spelling for x in node.get_tokens()])
    sp = ''.join(x.spelling for x in node.get_tokens()).split('=')
    assert len(sp) == 1 or len(sp) == 2
    # print("    ---> default =",   None if len(sp)==1 else sp[1])
    return None if len(sp) == 1 else sp[1]