Avoid copy in twist for tensors with bosonic braiding

Author: leburgel

src/tensors/indexmanipulations.jl

@@ -302,7 +302,10 @@ If `inv=true`, use the inverse twist.
 
 See [`twist!`](@ref) for storing the result in place.
 """
-twist(t::AbstractTensorMap, i; inv::Bool = false) = twist!(copy(t), i; inv)
+function twist(t::AbstractTensorMap, i; inv::Bool = false)
+    (BraidingStyle(sectortype(t)) == Bosonic() || isempty(is)) && return t
+    return twist!(copy(t), i; inv)
+end
 
 # Methods which change the number of indices, implement using `Val(i)` for type inference
 """