public Builder mergeDescription(com.google.devtools.cloudtrace.v2.TruncatableString value) {
          if (descriptionBuilder_ == null) {
            if (((bitField0_ & 0x00000001) != 0)
                && description_ != null
                && description_
                    != com.google.devtools.cloudtrace.v2.TruncatableString.getDefaultInstance()) {
              getDescriptionBuilder().mergeFrom(value);
            } else {
              description_ = value;
            }
          } else {
            descriptionBuilder_.mergeFrom(value);
          }
          if (description_ != null) {
            bitField0_ |= 0x00000001;
            onChanged();
          }
          return this;
        }
<pre>
A user-supplied message describing the event. The maximum length for
the description is 256 bytes.
</pre>

<code>.google.devtools.cloudtrace.v2.TruncatableString description = 1;</code>
java-trace/proto-google-cloud-trace-v2/src/main/java/com/google/devtools/cloudtrace/v2/Span.java