/* FILTER */
    /// Get FILTER column (nothing in htslib sadly)
    @property string filter()
    {
        const(char)[] ret;

        this.unpack(UnpackLevel.Filter);

        if (this.line.d.n_flt) {
            for(int i; i< this.line.d.n_flt; i++) {
                if (i) ret ~= ";";
                ret ~= fromStringz(this.vcfheader.hdr.id[BCF_DT_ID][ this.line.d.flt[0] ].key);
            }
        } else {
            ret = ".";
        }

        return ret.idup;
    }

                                                    this should be i |
                                                                     v
ret ~= fromStringz(this.vcfheader.hdr.id[BCF_DT_ID][ this.line.d.flt[0] ].key);