I'm getting the following error in my python code. Can you help me understand where I am going wrong? This is the error "The call rotate([0, 1, 3, 5]) returns [5, 0, 1, 3], not None. 

def rotate(alist):

"""

Rotates the contents of alist one element to the right.

Rotating a list to the right pushes all elements to the right, and makes

the previously last element the new first element.

Examples:

If a = [0,2,3,4], rotate(a) makes a = [4,0,2,3]

If a = [1], rotate(a) makes a = [1]

Parameter a: The list to rotate

Precondition: a non-empty list

"""

rotate_alist = []

for a in range(len(alist)):

rotate_alist.append(alist[(a-1) % len(alist)])

return rotate_alist