def METHOD_NAME(self, inputstore, templatefile=None, **kwargs):
    """converts a .po file to .xlf format"""
    if templatefile is None:
        outputstore = poxliff.PoXliffFile(**kwargs)
    else:
        outputstore = poxliff.PoXliffFile(templatefile, **kwargs)
    filename = inputstore.filename
    for inputunit in inputstore.units:
        if inputunit.isblank():
            continue
        self.convertunit(outputstore, inputunit, filename)
    return bytes(outputstore)