@classmethod
    def from_file(cls, filename):
        if os.path.exists(filename):
            fid = open(filename, "rb")
            try:
                return cls(cPickle.load(fid))
            finally:
                fid.close()
        else:
            return cls()
Create a new cursor, similar to the normal
dataset/ETHPy150Open cournape/Bento/bento/commands/dependency.py/CommandDataProvider.from_file--crossover with--dataset/ETHPy150Open blynch/CloudMemeBackend/gridfs/grid_file.py/GridOutCursor.__init__