diff --git a/src/operators/mpomultiline.jl b/src/operators/mpomultiline.jl
index f50e231d..07fcaa86 100644
--- a/src/operators/mpomultiline.jl
+++ b/src/operators/mpomultiline.jl
@@ -13,9 +13,7 @@ See also: [`Multiline`](@ref), [`SparseMPO`](@ref), [`DenseMPO`](@ref)
 """
 const MPOMultiline = Multiline{<:Union{SparseMPO,DenseMPO}}
 
-function MPOMultiline(Os::AbstractMatrix{<:MPOTensor})
-    return MPOMultiline(data, map(DenseMPO, eachrow(Os)))
-end
+MPOMultiline(Os::AbstractMatrix{<:MPOTensor}) = MPOMultiline(map(DenseMPO, eachrow(Os)))
 MPOMultiline(mpos::AbstractVector{<:Union{SparseMPO,DenseMPO}}) = Multiline(mpos)
 MPOMultiline(t::MPOTensor) = MPOMultiline(fill(t, 1, 1))
 
diff --git a/src/states/mpsmultiline.jl b/src/states/mpsmultiline.jl
index dd1fbf8a..e8f0845d 100644
--- a/src/states/mpsmultiline.jl
+++ b/src/states/mpsmultiline.jl
@@ -18,7 +18,9 @@ See also: [`Multiline`](@ref)
 """
 const MPSMultiline = Multiline{<:InfiniteMPS}
 MPSMultiline(mpss::AbstractVector{<:InfiniteMPS}) = Multiline(mpss)
-function MPSMultiline(pspaces::AbstractMatrix{S}, Dspaces::AbstractMatrix{S}; kwargs...) where {S<:VectorSpace}
+function MPSMultiline(
+    pspaces::AbstractMatrix{S}, Dspaces::AbstractMatrix{S}; kwargs...
+) where {S<:VectorSpace}
     data = map(eachrow(pspaces), eachrow(Dspaces)) do (p, D)
         return InfiniteMPS(p, D; kwargs...)
     end
@@ -30,8 +32,9 @@ function MPSMultiline(As::AbstractMatrix{T}; kwargs...) where {T<:GenericMPSTens
     end
     return MPSMultiline(data)
 end
-function MPSMultiline(ALs::AbstractMatrix{<:GenericMPSTensor}, 
-                      C₀::AbstractVector{<:MPSBondTensor}; kwargs...)
+function MPSMultiline(
+    ALs::AbstractMatrix{<:GenericMPSTensor}, C₀::AbstractVector{<:MPSBondTensor}; kwargs...
+)
     data = map(eachrow(ALs), C₀) do ALrow, C₀row
         return InfiniteMPS(ALrow, C₀row; kwargs...)
     end
diff --git a/src/utility/multiline.jl b/src/utility/multiline.jl
index 93d51201..70e769fe 100644
--- a/src/utility/multiline.jl
+++ b/src/utility/multiline.jl
@@ -39,3 +39,4 @@ function Base.circshift(A::Multiline, shifts::Tuple{Int,Int})
     return Multiline(circshift!(data′, shifts[1]))
 end
 Base.reverse(A::Multiline) = Multiline(reverse(parent(A)))
+Base.only(A::Multiline) = only(parent(A))
diff --git a/src/utility/utility.jl b/src/utility/utility.jl
index ce48b6de..1a9a1df4 100644
--- a/src/utility/utility.jl
+++ b/src/utility/utility.jl
@@ -142,4 +142,4 @@ end
 # check all elements are equal -> only defined in 1.8+
 @static if !isdefined(Base, :allequal)
     allequal(itr) = isempty(itr) ? true : all(isequal(first(itr)), itr)
-end
\ No newline at end of file
+end