Takes a v1.2 otuById dict and, for every otu,
    checks if ot:originalLabel exists. If it does not,
    but @label does, then ot:originalLabel is set to
    @label and @label is deleted.

def label_to_original_label_otu_by_id(otu_by_id):
    """Takes a v1.2 otuById dict and, for every otu,
    checks if ot:originalLabel exists. If it does not,
    but @label does, then ot:originalLabel is set to
    @label and @label is deleted.
    """
    for val in otu_by_id.values():
        orig = val.get('^ot:originalLabel')
        if orig is None:
            label = val.get('@label')
            if label:
                del val['@label']
                val['^ot:originalLabel'] = label