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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def fts_count(self, fts, inv):
 """Return the count of segments in an inventory matching a given feature mask. Args: fts (set):
 feature mask given as a set of (value, feature) tuples inv (set):
 inventory of segments (as Unicode IPA strings) Returns: int: number of segments in `inv` that match feature mask `fts` """

        return len(list(filter(lambda s: self.fts_match(fts, s), inv)))