def METHOD_NAME(env, target=None, source=_null, **kw):
    """Wrapper for _POFileBuilder. We use it to make user's life easier.
    This wrapper checks for `$POTDOMAIN` construction variable (or override in
    `**kw`) and treats it appropriatelly.
    """
    if source is _null:
        if 'POTDOMAIN' in kw:
            domain = kw['POTDOMAIN']
        elif 'POTDOMAIN' in env:
            domain = env['POTDOMAIN']
        else:
            domain = 'messages'
        source = [domain]  # NOTE: Suffix shall be appended automatically
    return env._POInitBuilder(target, source, **kw)