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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def listunion(ListOfLists):
 """ Take the union of a list of lists. Take a Python list of Python lists:: and return the aggregated list:: For a list of two lists, e.g. `[a, b]`, this is like:: a.extend(b) **Parameters** **ListOfLists** : Python list Python list of Python lists. **Returns** **u** : Python list Python list created by taking the union of the lists in `ListOfLists`. """

    u = []
    for s in ListOfLists:
        if s != None:
            u.extend(s)
    return u