docs: function _extract(req, param){
  
      var ret = [];
  
      // Note: no route parameter possible with lists(?).
  
      // Try the get space.
      if( req && req.query && typeof(req.query[param]) !== 'undefined' ){
  	//console.log('as query');
  
  	// Input as list, remove dupes.
  	var paccs = req.query[param];
  	if( paccs && ! us.isArray(paccs) ){
  	    paccs = [paccs];
  	}
  	ret = us.uniq(paccs);
      }
  
      // Otherwise, try the body space.
      if( us.isEmpty(ret) ){
  
  	var decoded_body = req.body || {};
  	if( decoded_body && ! us.isEmpty(decoded_body) && decoded_body[param] ){
  	    //console.log('as body');
  
  	    // Input as list, remove dupes.
  	    var baccs = decoded_body[param];
  	    //console.log('decoded_body', decoded_body);
  	    //console.log('baccs', baccs);
  	    if( baccs && ! us.isArray(baccs) ){
  		baccs = [baccs];
  	    }
  	    ret = us.uniq(baccs);
  	}
      }
  
      return ret;
  }