def assign_otu_membership(biomfile):
    """
    Determines the OTUIDs present in each sample.
    :type biomfile: biom.table.Table
    :param biomfile: BIOM table object from the biom-format library.
    :rtype: dict
    :return: Returns a dictionary keyed on Sample ID with sets containing
    the IDs of OTUIDs found in each sample.
    """
    samples = defaultdict(set)
    _ = biomfile.pa()
    for sid in biomfile.ids():
        for otuid in biomfile.ids("observation"):
            if biomfile.get_value_by_ids(otuid, sid) == 1:
                samples[sid].add(otuid)
    return samples