(self, fieldname, text)
Returns the total number of instances of the given term in the
        collection.
Returns the total number of instances of the given term in the
        collection.
Returns the total number of instances of the given term in the collection .
def frequency(self, fieldname, text):
        """Returns the total number of instances of the given term in the
        collection.
        """
        raise NotImplementedError
def frequency ( self , fieldname , text ) : raise NotImplementedError