public Builder setTargetGroupIndex(int value) {
            copyOnWrite();
            instance.setTargetGroupIndex(value);
            return this;
        }
<code>optional int32 target_group_index = 3;</code>

@param value The targetGroupIndex to set.
@return This builder for chaining.
turms-client-kotlin/src/main/java/im/turms/client/model/proto/request/user/relationship/DeleteRelationshipGroupMemberRequest.java