private void ensureThreatTypesIsMutable() {
      if (!((bitField0_ & 0x00000002) != 0)) {
        threatTypes_ = new java.util.ArrayList<java.lang.Integer>(threatTypes_);
        bitField0_ |= 0x00000002;
      }
    }
<pre>
A hash prefix, consisting of the most significant 4-32 bytes of a SHA256
hash. For JSON requests, this field is base64-encoded.
</pre>

<code>bytes hash_prefix = 1;</code>

@return This builder for chaining.
java-webrisk/proto-google-cloud-webrisk-v1beta1/src/main/java/com/google/webrisk/v1beta1/SearchHashesRequest.java