'Helper function to obtain the location of a corner of a bbox
Parameters
bbox : `matplotlib.transforms.Bbox`
loc : {1, 2, 3, 4}
Corner of *bbox*. Valid values are::
\'upper right\'  : 1,
\'upper left\'   : 2,
\'lower left\'   : 3,
\'lower right\'  : 4
Returns
x, y : float
Coordinates of the corner specified by *loc*.'

@staticmethod
def get_bbox_edge_pos(bbox, loc):

    (x0, y0, x1, y1) = bbox.extents
    if (loc == 1):
        return (x1, y1)
    elif (loc == 2):
        return (x0, y1)
    elif (loc == 3):
        return (x0, y0)
    elif (loc == 4):
        return (x1, y0)
