'Update the offset_text position based on the sequence of bounding
boxes of all the ticklabels'

def _update_offset_text_position(self, bboxes, bboxes2):

    (x, y) = self.offsetText.get_position()
    if (not len(bboxes)):
        bottom = self.axes.bbox.ymin
    else:
        bbox = mtransforms.Bbox.union(bboxes)
        bottom = bbox.y0
    self.offsetText.set_position((x, (bottom - ((self.OFFSETTEXTPAD * self.figure.dpi) / 72.0))))
