Write a python function to get the first element of each sublist.
def Extract(lst): 
    return [item[0] for item in lst] 
<s>[INST]<<SYS>>Given a task and its code, generate test cases for the code.<</SYS>>Write a python function to get the first element of each sublist.
def Extract(lst): 
    return [item[0] for item in lst] [/INST]assert Extract([[1, 2], [3, 4, 5], [6, 7, 8, 9]]) == [1, 3, 6]
assert Extract([[1,2,3],[4, 5]]) == [1,4]
assert Extract([[9,8,1],[1,2]]) == [9,1]</s>