correct eltype for BlockIterator

Author: lkdvos

src/tensors/blockiterator.jl

@@ -10,6 +10,6 @@ end
 
 Base.IteratorSize(::BlockIterator) = Base.HasLength()
 Base.IteratorEltype(::BlockIterator) = Base.HasEltype()
-Base.eltype(::Type{<:BlockIterator{T}}) where {T} = blocktype(T)
+Base.eltype(::Type{<:BlockIterator{T}}) where {T} = Pair{sectortype(T),blocktype(T)}
 Base.length(iter::BlockIterator) = length(iter.structure)
 Base.isdone(iter::BlockIterator, state...) = Base.isdone(iter.structure, state...)