private com.google.protobuf.MapFieldBuilder<
              java.lang.String,
              com.google.devtools.cloudtrace.v2.AttributeValueOrBuilder,
              com.google.devtools.cloudtrace.v2.AttributeValue,
              com.google.devtools.cloudtrace.v2.AttributeValue.Builder>
          internalGetMutableAttributeMap() {
        if (attributeMap_ == null) {
          attributeMap_ = new com.google.protobuf.MapFieldBuilder<>(attributeMapConverter);
        }
        bitField0_ |= 0x00000001;
        onChanged();
        return attributeMap_;
      }
<pre>
A set of attributes as key-value pairs.
</pre>

Protobuf type {@code google.devtools.cloudtrace.v2.Span.Attributes}
java-trace/proto-google-cloud-trace-v2/src/main/java/com/google/devtools/cloudtrace/v2/Span.java