public Builder mergeDatetimeValue(com.google.type.DateTime value) {
      if (datetimeValueBuilder_ == null) {
        if (valueCase_ == 3 && value_ != com.google.type.DateTime.getDefaultInstance()) {
          value_ =
              com.google.type.DateTime.newBuilder((com.google.type.DateTime) value_)
                  .mergeFrom(value)
                  .buildPartial();
        } else {
          value_ = value;
        }
        onChanged();
      } else {
        if (valueCase_ == 3) {
          datetimeValueBuilder_.mergeFrom(value);
        } else {
          datetimeValueBuilder_.setMessage(value);
        }
      }
      valueCase_ = 3;
      return this;
    }
<pre>
Datetime type value.
</pre>

<code>.google.type.DateTime datetime_value = 3;</code>
java-visionai/proto-google-cloud-visionai-v1/src/main/java/com/google/cloud/visionai/v1/FacetValue.java