How to use the gnomad.resources.grch37.gnomad_ld.ld_index.idx.collect function in gnomad

:param ld_index: Corresponding index table
    :param gene: Gene symbol as string
    :param vep_ht: Table with VEP annotations (if None, gets from get_gnomad_public_data())
    :param reference_genome: Reference genome to pass to get_gene_intervals for fast filtering to gene
    :return: Table with pairs of variants
    """
    if vep_ht is None:
        vep_ht = public_release('exomes').ht()
    if reference_genome is None:
        reference_genome = hl.default_reference().name
    intervals = hl.experimental.get_gene_intervals(gene_symbols=[gene], reference_genome=reference_genome)
    ld_index = hl.filter_intervals(ld_index, intervals)
    ld_index = ld_index.annotate(vep=vep_ht[ld_index.key].vep)
    ld_index = ld_index.filter(hl.any(lambda tc: tc.gene_symbol == gene, ld_index.vep.transcript_consequences))

    indices_to_keep = ld_index.idx.collect()
    filt_bm = bm.filter(indices_to_keep, indices_to_keep)
    ht = filt_bm.entries()
    ld_index = ld_index.add_index('new_idx').key_by('new_idx')
    return ht.transmute(r=ht.entry, i_variant=ld_index[ht.i], j_variant=ld_index[ht.j])