Async load in string format

I’m trying to figure out what string format should be for async loading. FStreamableManager::RequestAsyncLoad take an const TArray<FSoftObjectPath>& TargetsToStream argument. Following functions calls into the engine i found function FStreamableManager::StreamInternal with the same argument and following code.

			// We always queue a new request in case the existing one gets cancelled
			FString Package = TargetName.ToString();
			int32 FirstDot = Package.Find(TEXT("."));
			if (FirstDot != INDEX_NONE)
			{
				Package = Package.Left(FirstDot);
			}

			Existing->bAsyncLoadRequestOutstanding = true;
			Existing->bLoadFailed = false;
			LoadPackageAsync(Package, FLoadPackageAsyncDelegate::CreateSP(Handle, &FStreamableHandle::AsyncLoadCallbackWrapper, TargetName), Priority);

It takes everything before first dot and tries to load it instead, using full name for callback it seems.
Next function int32 LoadPackageAsync(const FString& InName, const FGuid* InGuid, const TCHAR* InPackageToLoadFrom, FLoadPackageAsyncDelegate InCompletionDelegate, EPackageFlags InPackageFlags , int32 InPIEInstanceID, int32 InPackagePriority) where InName is a chunk of my actual string and nPackageToLoadFrom always nullptr, since it’s looking for some variable in FAsyncPackage class i don’t have access to.
What I’m trying to achieve is to mount pak file, read map asset and load it. That wasn’t going to well so i thought i’d to simply load asset first.

In FPackageName when loading function FindPackageFileWithoutExtension check if file exist on disk by asking platform specific code for time stamps. Mounted files does not exist in the mounting point as i expected them to be, but function IterateDirectoryRecursively show that they exist in the mounting point.

What I tried to do was to load pak file from another project, and that is something not supported.