def reconstruct_path(start, dest, parents):
    """
    reconstruct_path reconstructs the shortest path from vertex
    start to vertex dest.

    "parents" is a dictionary which maps each vertex to their
    respective parent in the lowest cost path from start to that
    vertex.

    >>> parents = {'l': ' ', 'e': 'l', 'a': 'e', 'h':'a'}
    >>> reconstruct_path('l', 'h', parents)
    ['l', 'e', 'a', 'h']

    """
    current = dest
    path = [dest]

    while current != start:
        path.append(parents[current])
        current = parents[current]

    path.reverse()
    return path