def __init__(self, termset, maxchars = 200, charsbefore = 20, charsafter = 20):
        
        self.maxchars = maxchars
        self.charsbefore = charsbefore
        self.charsafter = charsafter
:termset: A collection (probably a set or frozenset) containing the
dataset/ETHPy150Open tallstreet/Whoosh-AppEngine/src/whoosh/highlight.py/ContextFragmenter.__init__