public Builder clearKey() {
      key_ = getDefaultInstance().getKey();
      bitField0_ = (bitField0_ & ~0x00000002);
      onChanged();
      return this;
    }
<pre>
Optional. Corresponds to the label key of a reservation resource. To target
a SPECIFIC_RESERVATION by name, use
`compute.googleapis.com/reservation-name` as the key and specify the name
of your reservation as its value.
</pre>

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

@return This builder for chaining.
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/ReservationAffinity.java