code: function getVersionsKeys(machineName) {
          let manifest = getManifest();
          if (!manifest.machines[machineName]) {
              throw new Error("Machine does not exists");
          }
          return Object.keys(manifest.machines[machineName].versions);
      }
docs: Get the keys of all of the versions of machine in the repository
  @method getVersionsKeys
  @param {String} machineName The name of the machine to get the version's keys
  @returns {Array} An array with all the version's keys of the machine