def find_start_end(grid):
    """
    Finds the source and destination block indexes from the list.

    Args
        grid:   <list>  the world grid blocks represented as a list of blocks (see Tutorial.pdf)

    Returns
        start: <int>   source block index in the list
        end:   <int>   destination block index in the list
    """
    start = grid.index(u'emerald_block')
    end = grid.index(u'redstone_block')
    return (start, end)