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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 tx2genedict(gtf, keep_version=False):
 """ produce a tx2gene dictionary from a GTF file """

    d = {}
    with open_gzipsafe(gtf) as in_handle:
        for line in in_handle:
            if "gene_id" not in line or "transcript_id" not in line:
                continue
            geneid = line.split("gene_id")[1].split(" ")[1]
            geneid = _strip_non_alphanumeric(geneid)
            txid = line.split("transcript_id")[1].split(" ")[1]
            txid = _strip_non_alphanumeric(txid)
            if keep_version and "transcript_version" in line:
                txversion = line.split("transcript_version")[1].split(" ")[1]
                txversion = _strip_non_alphanumeric(txversion)
                txid  += "." + txversion
            if has_transcript_version(line) and not keep_version:
                txid = _strip_feature_version(txid)
                geneid = _strip_feature_version(geneid)
            d[txid] = geneid
    return d