verb - To "keep" in this sense is the same as saying "I'm ok" or "I will be fine." It can be used in question form that would provoke such an answer as well.
This is first seen (as far as my research can tell) in page 6 of Penny Arcade's 'Automata'. The reader, form this implication, can be lead to believe that this term is specific only to robots ie automat, in the context of the story.
Yeah, I'll keep. I'm fine.