private void ensureNameServersIsMutable() {
        if (!nameServers_.isModifiable()) {
          nameServers_ = new com.google.protobuf.LazyStringArrayList(nameServers_);
        }
        bitField0_ |= 0x00000002;
      }
<pre>
Required. Domain used to resolve a `name_servers` list.
</pre>

<code>string domain = 1 [(.google.api.field_behavior) = REQUIRED];</code>

@param value The bytes for domain to set.
@return This builder for chaining.
java-vmwareengine/proto-google-cloud-vmwareengine-v1/src/main/java/com/google/cloud/vmwareengine/v1/DnsForwarding.java