public Builder setAllowedFunctionNames(int index, java.lang.String value) {
      if (value == null) {
        throw new NullPointerException();
      }
      ensureAllowedFunctionNamesIsMutable();
      allowedFunctionNames_.set(index, value);
      bitField0_ |= 0x00000002;
      onChanged();
      return this;
    }
<pre>
Optional. Function names to call. Only set when the Mode is ANY. Function
names should match [FunctionDeclaration.name]. With mode set to ANY, model
will predict a function call from the set of function names provided.
</pre>

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

@param index The index to set the value at.
@param value The allowedFunctionNames to set.
@return This builder for chaining.
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/FunctionCallingConfig.java