def listunion(ListOfLists):
u = []<EOL>for s in ListOfLists:<EOL><INDENT>if s != None:<EOL><INDENT>u.extend(s)<EOL><DEDENT><DEDENT>return u<EOL>
Take the union of a list of lists.

Take a Python list of Python lists::

        [[l11,l12, ...], [l21,l22, ...], ... , [ln1, ln2, ...]]

and return the aggregated list::

        [l11,l12, ..., l21, l22 , ...]

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`.