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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 _fixed_source_line(self):
 """Attempt to find the line that this node appears on. We need this method since not all nodes have :attr:`lineno` set. :returns: The line number of this node, or None if this could not be determined. :rtype: int or None """

        line = self.lineno
        _node = self
        try:
            while line is None:
                _node = next(_node.get_children())
                line = _node.lineno
        except StopIteration:
            _node = self.parent
            while _node and line is None:
                line = _node.lineno
                _node = _node.parent
        return line