private void ensureLinkIsMutable() {
        if (!((bitField0_ & 0x00000001) != 0)) {
          link_ = new java.util.ArrayList<com.google.devtools.cloudtrace.v2.Span.Link>(link_);
          bitField0_ |= 0x00000001;
        }
      }
<pre>
A collection of links, which are references from this span to a span
in the same or different trace.
</pre>

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