public Builder setKeyBytes(com.google.protobuf.ByteString value) {
      if (value == null) {
        throw new NullPointerException();
      }
      checkByteStringIsUtf8(value);
      key_ = value;
      bitField0_ |= 0x00000002;
      onChanged();
      return this;
    }
<pre>
Required. The key of this data schema. This key should be matching the key
of user specified annotation and unique inside corpus. This value can be up
to 63 characters, and valid characters are /[a-z][0-9]-/. The first
character must be a letter, the last could be a letter or a number.
</pre>

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

@param value The bytes for key to set.
@return This builder for chaining.
java-visionai/proto-google-cloud-visionai-v1/src/main/java/com/google/cloud/visionai/v1/DataSchema.java