Update Prefix_Sums.mdx

Author: SansPapyrus683

content/3_Silver/Prefix_Sums.mdx

@@ -270,9 +270,6 @@ public class Main {
 <PySection>
 
 ```py
-# import itertools
-
-
 def psum(a):
 	psum = [0]
 	for i in a:
@@ -290,9 +287,8 @@ for i in range(Q):
 ```
 
 An alternative approach is to use [`itertools.accumulate`](https://docs.python.org/3/library/itertools.html#itertools.accumulate).
-
-The first value returned is that of the iterable passed, so we add a zero in the front.
-Note that in newer versions you can give the optional parameter `initial=0`.
+Notice that we need to add a $0$ to the front of the array.
+If using a newer version, you can use the optional parameter `initial=0` as well.
 
 ```py
 import itertools