remove any bins that don't have 16S

def filter_missing_rna(s2bins, bins2s, rna_cov):
    """
    remove any bins that don't have 16S
    """
    for bin, scaffolds in list(bins2s.items()):
        c = 0
        for s in scaffolds:
            if s in rna_cov:
                c += 1
        if c == 0:
            del bins2s[bin]
    for scaffold, bin in list(s2bins.items()):
        if bin not in bins2s:
            del s2bins[scaffold]
    return s2bins, bins2s