def get_uniprot_evidence_level(header):
    """Returns uniprot protein existence evidence level for a fasta header.
    Evidence levels are 1-5, but we return 5 - x since sorting still demands
    that higher is better."""
    header = header.split()
    for item in header:
        item = item.split('=')
        try:
            if item[0] == 'PE':
                return 5 - int(item[1])
        except IndexError:
            continue
    return -1
Returns uniprot protein existence evidence level for a fasta header.
    Evidence levels are 1-5, but we return 5 - x since sorting still demands
    that higher is better.