public Builder setKey(java.lang.String value) {
      if (value == null) {
        throw new NullPointerException();
      }
      key_ = value;
      bitField0_ |= 0x00000001;
      onChanged();
      return this;
    }
<pre>
A unique key for this atom. Must be specified when using advanced
mapping.
</pre>

<code>string key = 1;</code>

@param value The key to set.
@return This builder for chaining.
java-video-transcoder/proto-google-cloud-video-transcoder-v1/src/main/java/com/google/cloud/video/transcoder/v1/EditAtom.java