from mrjob.job import MRJob
from mrjob.step import MRStep

class MRCoauthors(MRJob):
    def steps(self):
        # if you use multiple steps of MapReduce
        return [
            MRStep(mapper=self.mapper_parse, reducer=...),
            ...
        ]


    def mapper_parse(self, _, line):
        # read author, paper, citations from input line
        author, paper, citations = map(str.strip, line.split(','))
        citations = int(citations)
        # TODO: emit the appropriate key-value pairs

    # TODO: add more reducers / mappers as necessary


if __name__ == "__main__":
    MRCoauthors().run()