Function to remove elements from a list not working

[Girish Sahani]

Hi,
 I am trying to convert a list of pairs (l4) to list l5 by removing those
pairs from l4 which are not present in a third list called pairList.
 The following is a simplified part of the routine i have written. However
it does not give the correct output. Please help!
 Its possible i have made a trivial mistke since i am a newbie.

def getl5():
    l5 = []
    pairList = [[1,2],[3,4],[3,5],[3,6],[9,7],[8,9],[8,7],[7,9],[11,10]]
    l4 = [[4,2],[4,7],[4,10],[4,12],[9,2],[9,7],[9,10],[9,12],[11,2],[11,7]]
    for pair in l4:
        if pair not in pairList:
            element.remove(l4)
    l5.append(element)
    print "l5 is",l5