text: 'use strict';
  
  module.exports = {
    valideteId,
    fibonacci: fibonacci()
  };
  
  var ID_PREFIX = 'USER_';
  function valideteId (id) {
    return typeof id === 'string' && id.indexOf(ID_PREFIX) === 0;
  }
  
  function* fibonacci () {
    var n1 = 1;
    var n2 = 1;
  
    while (true) {
      var current = n2;
      n2 = n1;
      n1+= current;
      var reset = yield current;
      if (reset) {
        n1 = 1;
        n2 = 2;
      }
    }
  }
  