Block.edge_coordinates
- Block.edge_coordinates(edge, axes='xyz')
 Return the coordinates of the start and end point of an edge.
- Parameters:
 - edgetuple(int, int)
 The identifier of the edge.
- axesstr, optional
 The axes along which the coordinates should be included.
- Returns:
 - tuple(point, point)
 The coordinates of the start point. The coordinates of the end point.