code: function _get(key){
  	var ret = null;
  
  	// Pull from cache or re-read from fs.
  	//console.log('key: ' + key)
  	//console.log('use_zcache_p: ' + use_zcache_p)
  	if( use_zcache_p ){
  	    ret = zcache[key];
  	}else{
  	    ret = afs.read_file(path_cache[key]);
  	}
  
  	return ret;
      }
docs: Get a file, as string, from the cache by key; null otherwise.