'nth_coord = along which coordinate value varies
in 2d, nth_coord = 0 ->  x axis, nth_coord = 1 -> y axis'

def __init__(self, loc, nth_coord=None):

    self._loc = loc
    if (loc not in [u'left', u'right', u'bottom', u'top']):
        raise ValueError((u'%s' % loc))
    if (nth_coord is None):
        if (loc in [u'left', u'right']):
            nth_coord = 1
        elif (loc in [u'bottom', u'top']):
            nth_coord = 0
    self.nth_coord = nth_coord
    super(AxisArtistHelper.Fixed, self).__init__()
    self.passthru_pt = self._default_passthru_pt[loc]
    _verts = np.array([[0.0, 0.0], [1.0, 1.0]])
    fixed_coord = (1 - nth_coord)
    _verts[:, fixed_coord] = self.passthru_pt[fixed_coord]
    self._path = Path(_verts)
