please explain every step. thanms

01 def head (Q): 02 return o[O] 32 33 + R S = S + L returns 03 def tail(Q): 04 return 0[1:] 07 Here is how head, tail, and merresort head[3]) = 3 hail([3]) = ( head[[1,2,3]) = 1 tail[1,2,3]) = (2,3) mergesort|| 1) = [] meresort([1]) = [1] mergesort|(2,1]) = [1,2] 05 def mergesort (U): 06 if U == [l or tail(U) = []: return U 08 else: L = 1) R = 0 while True: if U = 0 : break else: L = L + [head (U)] U = tail(U) if U = 11: break else: R = R + [head (U) U = tail(U) L = mergesort (L) R = mergesert (R) S = ( while L != [] and R != []: if head (L)