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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_children(self):
 """Gets a new grouped symbol whose output contains inputs to output nodes of the original symbol. Example ------- <Symbol Grouped> ['x', '_plus10_output'] ['y', 'z'] Returns ------- sgroup : Symbol or None The children of the head node. If the symbol has no inputs then ``None`` will be returned. """

        handle = SymbolHandle()
        check_call(_LIB.MXSymbolGetChildren(
            self.handle, ctypes.byref(handle)))
        ret = Symbol(handle=handle)
        if len(ret.list_outputs()) == 0:
            return None
        return ret