From a line, return list of proteins reported by Mzid2TSV. When unrolled
    lines are given, this returns the single protein from the line.

def get_proteins_from_psm(line):
    """From a line, return list of proteins reported by Mzid2TSV. When unrolled
    lines are given, this returns the single protein from the line."""
    proteins = line[mzidtsvdata.HEADER_PROTEIN].split(';')
    outproteins = []
    for protein in proteins:
        prepost_protein = re.sub('\(pre=.*post=.*\)', '', protein).strip()
        outproteins.append(prepost_protein)
    return outproteins