+ {-# INLINE delete #-}
+ delete k (Headers m) = Headers $ delete k m
+ {-# INLINE member #-}
+ member k (Headers m) = member k m
+ {-# INLINE union #-}
+ union (Headers α) (Headers β)
+ = Headers $ union α β
+ {-# INLINE intersection #-}
+ intersection (Headers α) (Headers β)
+ = Headers $ intersection α β
+ {-# INLINE difference #-}
+ difference (Headers α) (Headers β)
+ = Headers $ difference α β
+ {-# INLINE isSubset #-}
+ isSubset (Headers α) (Headers β)
+ = isSubset α β
+ {-# INLINE isProperSubset #-}
+ isProperSubset (Headers α) (Headers β)
+ = isProperSubset α β