code: def listunion(ListOfLists):
      
      u = []
      for s in ListOfLists:
          if s != None:
              u.extend(s)
      return u
docs: 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`.