private void ensureScopeIsMutable() {
      if (!scope_.isModifiable()) {
        scope_ = new com.google.protobuf.LazyStringArrayList(scope_);
      }
      bitField0_ |= 0x00000002;
    }
<pre>
Email address of the service account. If empty, default Compute service
account will be used.
</pre>

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

@param value The bytes for email to set.
@return This builder for chaining.
java-tpu/proto-google-cloud-tpu-v2/src/main/java/com/google/cloud/tpu/v2/ServiceAccount.java