private com.google.protobuf.MapField<java.lang.Long, java.lang.Long> internalGetMutableMemberIdToReadDate() {
            if (memberIdToReadDate_ == null) {
                memberIdToReadDate_ = com.google.protobuf.MapField
                        .newMapField(MemberIdToReadDateDefaultEntryHolder.defaultEntry);
            }
            if (!memberIdToReadDate_.isMutable()) {
                memberIdToReadDate_ = memberIdToReadDate_.copy();
            }
            bitField0_ |= 0x00000002;
            onChanged();
            return memberIdToReadDate_;
        }
<code>int64 group_id = 1;</code>

@return This builder for chaining.
turms-server-common/src/main/java/im/turms/server/common/access/client/dto/model/conversation/GroupConversation.java