Getting Parse Server Session Token directly on iOS Swift

I recently migrated my application from Parse Server to my own custom server. I am trying to find a way to access the session token without having Parse SDK imported on my project. I need the session token, so I do not have to re-authenticate my current logged in users.

So far I access it with the following methods, that requires to import parse sdk:

        PFUser.current()?.saveInBackground(block: { [weak self] (success, error) in
            if let error = error {
                Log.error?.message(error.localizedDescription)
                return
            }
            guard let sessionToken = PFUser.current()?.sessionToken else {
                Log.error?.message("Did not get session token even after saving user")
                return
            }
        })

The other solution I was looking at is the private documents directory of parse, but I could only get applicationId, installationId and config from there:

class ParseHelper {    
    var parsePrivateDocumentsDirectory: URL? {
        let filemanager = FileManager.default
        guard let libraryDirectory = filemanager.urls(for: .libraryDirectory, in: .userDomainMask).last else {
            return nil
        }

        guard let parseDirectory = URL(string: "Private%20Documents/Parse/", relativeTo: libraryDirectory) else {
            return nil
        }
        return parseDirectory
    }

    func parseFile(_ filename: String) -> URL? {
        let filemanager = FileManager.default
        guard let parseDirectory = self.parsePrivateDocumentsDirectory else {
            return nil
        }

        guard let installationIdUrl = URL(string: filename, relativeTo: parseDirectory) else {
            return nil
        }

        if filemanager.fileExists(atPath: installationIdUrl.path) {
            return installationIdUrl
        } else {
            return nil
        }
    }

    var installationId: String? {
        guard let fileURL = self.parseFile("installationId"), let data = try? Data(contentsOf: fileURL) else {
            return nil
        }
        let string = String(data: data, encoding: String.Encoding.utf8)
        return string
    }

    var applicationId: String? {
        guard let fileURL = self.parseFile("applicationId"), let data = try? Data(contentsOf: fileURL) else {
            return nil
        }
        let string = String(data: data, encoding: String.Encoding.utf8)
        return string
    }

    var config: String? {
        guard let fileURL = self.parseFile("config"), let data = try? Data(contentsOf: fileURL) else {
            return nil
        }
        let string = String(data: data, encoding: String.Encoding.utf8)
        return string
    }
}