public com.google.protobuf.ByteString getExternalIdBytes() {
      java.lang.Object ref = externalId_;
      if (ref instanceof String) {
        com.google.protobuf.ByteString b =
            com.google.protobuf.ByteString.copyFromUtf8((java.lang.String) ref);
        externalId_ = b;
        return b;
      } else {
        return (com.google.protobuf.ByteString) ref;
      }
    }
<pre>
Required. Client side tenant identifier, used to uniquely identify the
tenant.

The maximum number of allowed characters is 255.
</pre>

<code>string external_id = 2 [(.google.api.field_behavior) = REQUIRED];</code>

@return The bytes for externalId.
java-talent/proto-google-cloud-talent-v4beta1/src/main/java/com/google/cloud/talent/v4beta1/Tenant.java