public Builder setGroupIndex(long value) {
            copyOnWrite();
            instance.setGroupIndex(value);
            return this;
        }
<code>optional int64 group_index = 4;</code>

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