getMandatorySlots(intent) {
    const result = {};
    const intentSlots = this.intents[intent];
    if (intentSlots) {
      const keys = Object.keys(intentSlots);
      for (let i = 0, l = keys.length; i < l; i += 1) {
        const slot = intentSlots[keys[i]];
        if (slot.mandatory) {
          result[slot.entity] = slot;
        }
      }
    }
    return result;
  }
Given an intent return the mandatory slots.
@param {String} intent Name of the intent
@returns {Object} Object with the mandatory slots.