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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 _is_level_reference(self, key, axis=0):
 """ Test whether a key is a level reference for a given axis. To be considered a level reference, `key` must be a string that: - (axis=0):
 Matches the name of an index level and does NOT match a column label. - (axis=1):
 Matches the name of a column level and does NOT match an index label. Parameters key : str Potential level name for the given axis axis : int, default 0 Axis that levels are associated with (0 for index, 1 for columns) Returns ------- is_level : bool """

        axis = self._get_axis_number(axis)

        if self.ndim > 2:
            raise NotImplementedError(
                "_is_level_reference is not implemented for {type}"
                .format(type=type(self)))

        return (key is not None and
                is_hashable(key) and
                key in self.axes[axis].names and
                not self._is_label_reference(key, axis=axis))