'Copies the file to a destination files and returns it.'

def _copy_file(self, destination, overwrite=False):

    if overwrite:
        raise NotImplementedError
    src_file_name = self.file.name
    storage = self.file.storages[(u'public' if self.is_public else u'private')]
    src_file = storage.open(src_file_name)
    src_file.open()
    return storage.save(destination, ContentFile(src_file.read()))
