private com.google.protobuf.SingleFieldBuilderV3<
            com.google.devtools.cloudtrace.v2.Span.Attributes,
            com.google.devtools.cloudtrace.v2.Span.Attributes.Builder,
            com.google.devtools.cloudtrace.v2.Span.AttributesOrBuilder>
        getAttributesFieldBuilder() {
      if (attributesBuilder_ == null) {
        attributesBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.devtools.cloudtrace.v2.Span.Attributes,
                com.google.devtools.cloudtrace.v2.Span.Attributes.Builder,
                com.google.devtools.cloudtrace.v2.Span.AttributesOrBuilder>(
                getAttributes(), getParentForChildren(), isClean());
        attributes_ = null;
      }
      return attributesBuilder_;
    }
<pre>
A set of attributes on the span. You can have up to 32 attributes per
span.
</pre>

<code>.google.devtools.cloudtrace.v2.Span.Attributes attributes = 7;</code>
java-trace/proto-google-cloud-trace-v2/src/main/java/com/google/devtools/cloudtrace/v2/Span.java