mple data types are available as field types, including <code>bool</code>, <code>int32</code>, <code>float</code>, <code>double</code>, and <code>string.</code> You can also add further structure to your messages by using other message types as field types – in the above example the <code>Person</code> message contains <code>PhoneNumber</code> messages, while the <code>AddressBook</code> message contains <code>Person</code> messages. You can even define message types nested inside other messages – as yo