docs: @Nonnull
    public JSDefinedClass removeField (@Nonnull final JSFieldVar aField)
    {
      ValueEnforcer.notNull (aField, "Field");
  
      if (m_aFields.remove (aField.name ()) != aField)
        throw new IllegalArgumentException ("Failed to remove field '" +
                                            aField.name () +
                                            "' from " +
                                            m_aFields.keySet ());
      return this;
    }