hould be placed:

            - 'pre': The y value is continued constantly to the left from
              every *x* position, i.e. the interval ``(x[i-1], x[i]]`` has the
              value ``y[i]``.
            - 'post': The y value is continued constantly to the right from
              every *x* position, i.e. the interval ``[x[i], x[i+1])`` has the
              value ``y[i]``.
            - 'mid': Steps occur half-way between the *x* positions.

        data : indexable object, optional
            An object with labelled data. If given, provide the label names to
            plot in *x* and *y*.

        **kwargs
            Additional parameters are the same as those for `.plot`.

        Returns
        -------
        list of `.Line2D`
            Objects representing the plotted data.
        )