human
4 Bit Ripple Carry
myHDL Code"
Please write code following the instructions in jupyter notebook style.
 ... What is a code to 4 Bit Ripple Carry and the other steps required?
assistant
#Here is code to 4 Bit Ripple Carry and the other steps required.

@block
def RippleCarry4Bit(X1, X2, cin, S, c):
    """
    4 Bit Ripple Carray Adder
    Input:
    Output:
    """
    
    S_i = [Signal(bool(0)) for _ in range(len(S))]   # Sum bit for each stage.
    
    #create intercontect wire between FA0 and FA1 and intialze FA0 and wire up
    c_FA0FA1=Signal(bool(0))
    FA0=FullAdder(x1=X1(0), x2=X2(0), cin=cin, s=S_i[0], c=c_FA0FA1)
    
    c_FA1FA2=Signal(bool(0))
    FA1=FullAdder(x1=X1(1), x2=X2(1), cin=c_FA0FA1, s=S_i[1], c=c_FA1FA2)
    
    c_FA2FA3=Signal(bool(0))
    FA2=FullAdder(x1=X1(2), x2=X2(2), cin=c_FA1FA2, s=S_i[2], c=c_FA2FA3)
    
    FA3=FullAdder(x1=X1(3), x2=X2(3), cin=c_FA2FA3, s=S_i[3], c=c)

    #concat bus wires to single bitvec wire
    @always_comb
    def ConCatSum():
        S.next=concat(S_i[3], S_i[2], S_i[1], S_i[0])

    
    return instances()