code: function PreLoadCondition (meta, preLoadConditionFn) {
    Definition.call(this, meta);
  
    meta = meta || {};
  
    if (!preLoadConditionFn || !_.isFunction(preLoadConditionFn)) {
      var err = new Error('Pre-load-condition function not injected!');
      debug(err);
      throw err;
    }
  
    this.description = meta.description;
    this.version = meta.version;
    this.payload = meta.payload || null;
    this.priority = meta.priority || Infinity;
  
    this.preLoadConditionFn = preLoadConditionFn;
  }
docs: PreLoadCondition constructor
  @param {Object}   meta  Meta infos like: { name: 'name', version: 1, priority: 1, payload: 'some.path', description: 'bla bla' }
  @param {Function} preLoadConditionFn Function handle
  `function(command, aggData, callback){}`
  @constructor