'label reference position in transAxes.
get_label_transform() returns a transform of (transAxes+offset)'

def get_axislabel_pos_angle(self, axes):

    loc = self._axis_direction
    if (self.nth_coord == 0):
        angle = 0
    else:
        angle = 90
    _verts = [0.5, 0.5]
    fixed_coord = (1 - self.nth_coord)
    trans_passingthrough_point = (axes.transData + axes.transAxes.inverted())
    p = trans_passingthrough_point.transform_point([self._value, self._value])
    _verts[fixed_coord] = p[fixed_coord]
    if (not (0.0 <= _verts[fixed_coord] <= 1.0)):
        return (None, None)
    else:
        return (_verts, angle)
