def _preferred_filetype(self, filetypes):
        """Get the preferred filetype out of the *filetypes* list.

        At the moment, it just returns the first filetype that has been loaded.
        """
        if not isinstance(filetypes, list):
            filetypes = [filetypes]

        # look through the file types and use the first one that we have loaded
        for filetype in filetypes:
            if filetype in self.file_handlers:
                return filetype
        return None
Get the preferred filetype out of the *filetypes* list.

        At the moment, it just returns the first filetype that has been loaded.