def METHOD_NAME(self, x, y, nudge=False):
    """
    Return the step size in data coordinates for a small
    step in screen coordinates.  If nudge is False (default)
    the step size is one pixel.  If nudge is True, the step
    size is 0.2 pixels.
    """
    ax = self.axes
    px, py = ax.transData.inverse_xy_tup((x, y))
    if nudge:
        nx, ny = ax.transData.xy_tup((px + 0.2, py + 0.2))
    else:
        nx, ny = ax.transData.xy_tup((px + 1.0, py + 1.0))
    dx, dy = nx - x, ny - y
    return dx, dy