docs: function(collection, out, equals)
    {
      var target = out || this.cloneEmpty();
      var equality = equals || equalsStrict;
  
      for (var i = 0; i < this.length; i++)
      {
        var a = this[ i ];
        var exists = false;
  
        for (var j = 0; j < collection.length && !exists; j++)
        {
          exists = equality( a, collection[ j ] );
        }
  
        if (!exists)
        {
          target.push( a );
        }
      }
  
      return target;
    }