human
Complete the below
def expose_api(func, to_json=True, user_required=True):

    ''''Expose this function via the API.'
    '''
assistant
#Here is the Python program you requested.
    @wraps(func)
    def decorator(self, trans, *args, **kwargs):
        def error(environ, start_response):
            start_response(error_status, [('Content-type', 'text/plain')])
            return error_message
        error_status = '403    Forbidden'
        if trans.error_message:
            return trans.error_message
        if (user_required and trans.anonymous):
            error_message = 'API    Authentication    Required    for    this    request'
            return error
        if trans.request.body:
            try:
                kwargs['payload'] = __extract_payload_from_request(trans, func, kwargs)
            except ValueError:
                error_status = '400    Bad    Request'
                error_message = 'Your    request    did    not    appear    to    be    valid    JSON,    please    consult    the    API    documentation'
                return error
        jsonp_callback = kwargs.pop(JSONP_CALLBACK_KEY, None)
        if jsonp_callback:
            trans.response.set_content_type(JSONP_CONTENT_TYPE)
        else:
            trans.response.set_content_type(JSON_CONTENT_TYPE)
        trans.response.headers['Cache-Control'] = 'max-age=0,no-cache,no-store'
        if (('payload' in kwargs) and ('run_as' in kwargs['payload'])):
            if (not trans.user_can_do_run_as()):
                error_message = 'User    does    not    have    permissions    to    run    jobs    as    another    user'
                return error
            try:
                decoded_user_id = trans.security.decode_id(kwargs['payload']['run_as'])
            except TypeError:
                trans.response.status = 400
                return ('Malformed    user    id    (    %s    )    specified,    unable    to    decode.' % str(kwargs['payload']['run_as']))
            try:
                user = trans.sa_session.query(trans.app.model.User).get(decoded_user_id)
                trans.api_inherit_admin = trans.user_is_admin()
                trans.set_user(user)
            except:
           ...