Apply suggestions from code review for preprocessor

Co-authored-by: Jutho <Jutho@users.noreply.github.com>

Author: kshyatt

src/planar/preprocessors.jl

@@ -83,20 +83,12 @@ _add_adjoint(ex) = Expr(TO.prime, ex)
 # spaces from the rest of the expression. Construct the explicit BraidingTensor objects and
 # insert them in the expression.
 function _construct_braidingtensors(ex)
-    function filter_f(expr)
-        if TO.istensor(expr)
-            return _remove_adjoint(TO.decomposetensor(expr)[1]) != :τ
-        elseif TO.istensorexpr(expr)
-            return any(filter_f, expr.args)
-        else
-            return false
-        end
-    end
     function extract_tensors(tensor_ex)
         if TO.istensor(tensor_ex)
-            return [TO.decomposetensor(tensor_ex)[1]]
+            obj = TO.decomposetensor(expr)[1]
+            return (_remove_adjoint(obj) == :τ) ? Any[] : Any[obj]
         elseif TO.istensorexpr(tensor_ex)
-            return collect(Iterators.flatmap(extract_tensors, filter(filter_f, tensor_ex.args)))
+            return collect(Any, Iterators.flatmap(extract_tensors, tensor_ex.args))
         end
     end
     # get storagetype
@@ -122,7 +114,7 @@ function _construct_braidingtensors(ex)
             end
         end
         # if this is a definition, the lhs tensor is NOT yet defined
-        no_τ_ex = reduce(vcat, Iterators.flatmap(extract_tensors, filter(filter_f, rhs.args)); init = Symbol[])
+        no_τ_ex = collect(Any, Iterators.flatmap(extract_tensors, rhs.args))
         newrhs, success = _construct_braidingtensors!(rhs, preargs, indexmap, no_τ_ex)
         success ||
             throw(ArgumentError("cannot determine the spaces of all braiding tensors in $ex"))
@@ -134,7 +126,7 @@ function _construct_braidingtensors(ex)
     elseif TO.istensorexpr(ex)
         preargs = Vector{Any}()
         indexmap = Dict{Any, Any}()
-        no_τ_ex = reduce(vcat, Iterators.flatmap(extract_tensors, filter(filter_f, ex.args)); init = Symbol[])
+        no_τ_ex = collect(Any, Iterators.flatmap(extract_tensors, ex.args))
         newex, success = _construct_braidingtensors!(ex, preargs, indexmap, no_τ_ex)
         success ||
             throw(ArgumentError("cannot determine the spaces of all braiding tensors in $ex"))