_setFactValue (fact, params, value) {
    const cacheKey = fact.getCacheKey(params)
    const factValue = Promise.resolve(value)
    if (cacheKey) {
      this.factResultsCache.set(cacheKey, factValue)
    }
    return factValue
  }
Sets the computed value of a fact
@param {Fact} fact
@param {Object} params - values for differentiating this fact value from others, used for cache key
@param {Mixed} value - computed value