def y_str(y):
    """
    Takes a label vector, y, and returns a pretty string representation of it.
    """
    s = "[ "
    s += "A betrays B this turn: " + str(y[0]) + ", "
    s += "A betrays B next turn: " + str(y[1]) + ", "
    s += "A betrays B turn after next: " + str(y[2]) + ", "
    s += "B betrays A this turn: " + str(y[3]) + ", "
    s += "B betrays A next turn: " + str(y[4]) + ", "
    s += "B betrays A turn after next: " + str(y[5])
    s += " ]"
    return s