code: function getAsyncFncWrapper(asyncFncWrapper){
      if(!asyncFncWrapper) return setImmediate;
      else if(asyncFncWrapper === true) return function(cb){ cb(); };
      else if(!(asyncFncWrapper === setImmediate ||
                asyncFncWrapper === setTimeout ||
                typeof asyncFncWrapper === 'function')){
          
          throw new Error('Wrong argument "asyncFncWrapper", it have to be function, setImmediate, setTimeout, ' +
                          'or true when use default function, or undefined to use setImmediate');
      }
      
      return asyncFncWrapper;
  }
docs: /*
  helper for getting asyncFncWrapper
  @param {Object} asyncFncWrapper Description
  @returns {Object}  Description