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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def map_to_subset(self, file, outfile=None, ontology=None, subset=None, class_map=None, relations=None):
 """ Map a file to a subset, writing out results You can pass either a subset name (e.g. goslim_generic) or a dictionary with ready-made mappings Arguments --------- file: file Name or file object for input assoc file outfile: file Name or file object for output (mapped) assoc file; writes to stdout if not set subset: str Optional name of subset to map to, e.g. goslim_generic class_map: dict Mapping between asserted class ids and ids to map to. Many to many ontology: `Ontology` Ontology to extract subset from """

        if subset is not None:
            logging.info("Creating mapping for subset: {}".format(subset))
            class_map = ontology.create_slim_mapping(subset=subset, relations=relations)

        if class_map is None:
            raise ValueError("Neither class_map not subset is set")
        col = self.ANNOTATION_CLASS_COLUMN
        file = self._ensure_file(file)
        tuples = []
        for line in file:
            if line.startswith("!"):
                continue
            vals = line.split("\t")
            logging.info("LINE: {} VALS: {}".format(line, vals))
            if len(vals) < col:
                raise ValueError("Line: {} has too few cols, expect class id in col {}".format(line, col))
            cid = vals[col]
            if cid not in class_map or len(class_map[cid]) == 0:
                self.report.error(line, Report.UNMAPPED_ID, cid)
                continue
            else:
                for mcid in class_map[cid]:
                    vals[col] = mcid
                    line = "\t".join(vals)
                    if outfile is not None:
                        outfile.write(line)
                    else:
                        print(line)