'Returns a FramesMatches object obtained by filtering out the FramesMatch
which do not satistify the condition ``cond``. ``cond`` is a function
(FrameMatch -> bool).
Examples
>>> # Only keep the matches corresponding to (> 1 second) sequences.
>>> new_matches = matches.filter( lambda match: match.time_span > 1)'

def filter(self, cond):

    return FramesMatches(filter(cond, self))
