returning True, False or None

[Steven Bethard]

I have lists containing values that are all either True, False or None, 
e.g.:

     [True,  None,  None,  False]
     [None,  False, False, None ]
     [False, True,  True,  True ]
     etc.

For a given list:
* If all values are None, the function should return None.
* If at least one value is True, the function should return True.
* Otherwise, the function should return False.

Right now, my code looks like:

     if True in lst:
         return True
     elif False in lst:
         return False
     else:
         return None

This has a light code smell for me though -- can anyone see a simpler 
way of writing this?

STeVe