code: function mixin( key, val ){
  
          if ( typeof key === 'object' ){
              proto = extend(proto, key);
              proto.type = type;
              return;
          }
  
          if ( key !== 'type' && Physics.util.isFunction( val ) ){
              proto[ key ] = val;
          }
      }
docs: /*
  mixin( key, val )
  mixin( obj )
  - key (String): The method name
  - val (Function): The function to assign
  - obj (Object): object with many `key: fn` pairs
  
  Apply mixin methods to decorator base.