public Builder clearAttachmentIdStr() {
            attachmentIdStr_ = getDefaultInstance().getAttachmentIdStr();
            bitField0_ &= ~0x00000002;
            onChanged();
            return this;
        }
<code>optional string attachment_id_str = 2;</code>

@return This builder for chaining.
turms-server-common/src/main/java/im/turms/server/common/access/client/dto/request/storage/UpdateMessageAttachmentInfoRequest.java