'Return the ordered widening points for a specific function.
:param int function_address: Address of the querying function.
:return: A list of sorted merge points (addresses).
:rtype: list'

def _widening_points(self, function_address):

    try:
        new_function = self.kb.functions[function_address]
    except KeyError:
        return []
    if (function_address not in self._function_widening_points):
        if (not new_function.normalized):
            new_function.normalize()
        widening_points = CFGUtils.find_widening_points(function_address, new_function.endpoints, new_function.graph)
        self._function_widening_points[function_address] = widening_points
    return self._function_widening_points[function_address]
