def get_neighbors_of(cell):
    """
    Return the neighbors of cell.
    """
    x, y = cell
    neighbors = []

    distance = 1
    r = range(0 - distance, 1 + distance)
    for row in r:
        for col in r:
            if not row == col == 0:
                neighbors.append((x + row, y + col))

    return set(neighbors)