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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 line_stack(self, x, y, **kw):
        ''' Generate multiple ``Line`` renderers for lines stacked vertically
        or horizontally.

        Args:
            x (seq[str]) :

            y (seq[str]) :

        Additionally, the ``name`` of the renderer will be set to
        the value of each successive stacker (this is useful with the
        special hover variable ``$name``)

        Any additional keyword arguments are passed to each call to ``hbar``.
        If a keyword value is a list or tuple, then each call will get one
        value from the sequence.

        Returns:
            list[GlyphRenderer]

        Examples:

            Assuming a ``ColumnDataSource`` named ``source`` with columns
            *2106* and *2017*, then the following call to ``line_stack`` with
            stackers for the y-coordinates will will create two ``Line``
            renderers that stack:

            .. code-block:: python

                p.line_stack(['2016', '2017'], x='x', color=['blue', 'red'], source=source)

            This is equivalent to the following two separate calls:

            .. code-block:: python

                p.line(y=stack('2016'),         x='x', color='blue', source=source, name='2016')
                p.line(y=stack('2016', '2017'), x='x', color='red',  source=source, name='2017')

        '''
        if all(isinstance(val, (list, tuple)) for val in (x,y)):
            raise ValueError("Only one of x or y may be a list of stackers")

        result = []

        if isinstance(y, (list, tuple)):
            kw['x'] = x
            for kw in _single_stack(y, "y", **kw):
                result.append(self.line(**kw))
            return result

        if isinstance(x, (list, tuple)):
            kw['y'] = y
            for kw in _single_stack(x, "x", **kw):
                result.append(self.line(**kw))
            return result

        return [self.line(x, y, **kw)]