public Builder mergeAttributes(com.google.devtools.cloudtrace.v2.Span.Attributes value) {
          if (attributesBuilder_ == null) {
            if (((bitField0_ & 0x00000002) != 0)
                && attributes_ != null
                && attributes_
                    != com.google.devtools.cloudtrace.v2.Span.Attributes.getDefaultInstance()) {
              getAttributesBuilder().mergeFrom(value);
            } else {
              attributes_ = value;
            }
          } else {
            attributesBuilder_.mergeFrom(value);
          }
          if (attributes_ != null) {
            bitField0_ |= 0x00000002;
            onChanged();
          }
          return this;
        }
<pre>
A set of attributes on the annotation. You can have up to 4 attributes
per Annotation.
</pre>

<code>.google.devtools.cloudtrace.v2.Span.Attributes attributes = 2;</code>
java-trace/proto-google-cloud-trace-v2/src/main/java/com/google/devtools/cloudtrace/v2/Span.java