builtins.ValueError: Method 'f1' not found in: <amazon_spider 'amazon

 I've a decorator function:

def check_response(f):
    '''decorator for the parse functions. Checks if we're banned or not.'''
    def f1(self, response):
        ...
    return f1

 And I use it for parse callbacks:

    @check_response
    def parse_qa(self, response):        

It works ok locally, but emits the following error on ScrapingHub:

Traceback (most recent call last):
  File "/app/python/lib/python3.6/site-packages/scrapy/commands/crawl.py", line 58, in run
    self.crawler_process.start()
  File "/app/python/lib/python3.6/site-packages/scrapy/crawler.py", line 285, in start
    reactor.run(installSignalHandlers=False)  # blocking call
  File "/app/python/lib/python3.6/site-packages/twisted/internet/base.py", line 1243, in run
    self.mainLoop()
  File "/app/python/lib/python3.6/site-packages/twisted/internet/base.py", line 1252, in mainLoop
    self.runUntilCurrent()
--- <exception caught here> ---
  File "/app/python/lib/python3.6/site-packages/twisted/internet/base.py", line 878, in runUntilCurrent
    call.func(*call.args, **call.kw)
  File "/app/python/lib/python3.6/site-packages/scrapy/utils/reactor.py", line 41, in __call__
    return self._func(*self._a, **self._kw)
  File "/app/python/lib/python3.6/site-packages/scrapy/core/engine.py", line 122, in _next_request
    if not self._next_request_from_scheduler(spider):
  File "/app/python/lib/python3.6/site-packages/scrapy/core/engine.py", line 149, in _next_request_from_scheduler
    request = slot.scheduler.next_request()
  File "/app/python/lib/python3.6/site-packages/scrapy/core/scheduler.py", line 71, in next_request
    request = self._dqpop()
  File "/app/python/lib/python3.6/site-packages/scrapy/core/scheduler.py", line 108, in _dqpop
    return request_from_dict(d, self.spider)
  File "/app/python/lib/python3.6/site-packages/scrapy/utils/reqser.py", line 50, in request_from_dict
    cb = _get_method(spider, cb)
  File "/app/python/lib/python3.6/site-packages/scrapy/utils/reqser.py", line 87, in _get_method
    raise ValueError("Method %r not found in: %s" % (name, obj))
builtins.ValueError: Method 'f1' not found in: <amazon_spider 'amazon' at 0x7f82b45d2f60>