+ {-# INLINE empty #-}
+ empty
+ = Headers empty
+ {-# INLINE singleton #-}
+ singleton v
+ = Headers $ singleton v
+ {-# INLINE insertMany #-}
+ insertMany f (Headers m)
+ = Headers $ insertMany f m
+ {-# INLINE insertManySorted #-}
+ insertManySorted f (Headers m)
+ = Headers $ insertManySorted f m