Multiple parameters within response.meta.get()
response.meta in scrapy it's just a normal python dict, and as a python dict it has the method get which is None safe - when the second parameter is a default value that take place in case the first parameter is not in the dict.
for example:
while response.meta['unknown_key'] will raise KeyError exception,
response.meta.get('unknown_key') will return None, and 
response.meta.get('unknown_key', 'abc') will return abc
Is there any solid refernce as to how multiple parameters can fit within response.meta.get("something","someotherthing")in scrapy? If it is posible then how someotherthing relates to something?
I searched a lot but could not find anywhere the exact answer I'm after.