public Builder setKeyBytes(com.google.protobuf.ByteString value) {
        if (value == null) {
          throw new NullPointerException();
        }
        checkByteStringIsUtf8(value);
        key_ = value;
        bitField0_ |= 0x00000001;
        onChanged();
        return this;
      }
<pre>
The key of the label attached to the product. Cannot be empty and cannot
exceed 128 bytes.
</pre>

<code>string key = 1;</code>

@param value The bytes for key to set.
@return This builder for chaining.
java-vision/proto-google-cloud-vision-v1p3beta1/src/main/java/com/google/cloud/vision/v1p3beta1/Product.java