Merge sort part 1

merge_sort_1.py

def MergeSort(a):
    """ 
    Takes a list, returns a list.
    """
    if (len(a) < 2): 
        return a
    else:
        mid = (len(a)) / 2 
        left = a[:mid]
        right = a[mid:]
    left = MergeSort(left)
    right = MergeSort(right)
    return Merge(left, right)