title: Is it possible to define mandatory statements in any order in ANTLR4?
body: <p>Is it possible to define mandatory statements in any order in ANTLR4?</p>
  
  <p>If I do</p>
  
  <pre><code> module_header_stmts :  (
        yang_version_stmt stmtsep
      | namespace_stmt stmtsep
      | prefix_stmt stmtsep
   )+ ;
  </code></pre>
  
  <p>it's OK for any order of statements, but they're not mandatory as I would need.</p>
  
  <p>If I do </p>
  
  <pre><code> module_header_stmts :  
         yang_version_stmt stmtsep
         namespace_stmt stmtsep
         prefix_stmt stmtsep
   ;
  </code></pre>
  
  <p>then all of them are mandatory, but I can't give them any order.
  Any help?</p>