Updated doc (#572)

* Update website/docs/FAQ.md

website/docs/FAQ.md

@@ -5,7 +5,7 @@
 - Definition and purpose: The `low_cost_partial_config` is a dictionary of subset of the hyperparameter coordinates whose value corresponds to a configuration with known low-cost (i.e., low computation cost for training the corresponding model).  The concept of low/high-cost is meaningful in the case where a subset of the hyperparameters to tune directly affects the computation cost for training the model. For example, `n_estimators` and `max_leaves` are known to affect the training cost of tree-based learners. We call this subset of hyperparameters, *cost-related hyperparameters*. In such scenarios, if you are aware of low-cost configurations for the cost-related hyperparameters, you are recommended to set them as the `low_cost_partial_config`. Using the tree-based method example again, since we know that small `n_estimators` and  `max_leaves` generally correspond to simpler models and thus lower cost, we set `{'n_estimators': 4, 'max_leaves': 4}` as the `low_cost_partial_config` by default (note that `4` is the lower bound of search space for these two hyperparameters), e.g., in [LGBM](https://github.com/microsoft/FLAML/blob/main/flaml/model.py#L215).  Configuring `low_cost_partial_config` helps the search algorithms make more cost-efficient choices.  
 In AutoML, the `low_cost_init_value` in `search_space()` function for each estimator serves the same role.
 
-- Usage in practice: It is recommended to configure it if there are cost-related hyperparameters in your tuning task and you happen to know the low-cost values for them, but it is not required( It is fine to leave it the default value, i.e., `None`).
+- Usage in practice: It is recommended to configure it if there are cost-related hyperparameters in your tuning task and you happen to know the low-cost values for them, but it is not required (It is fine to leave it the default value, i.e., `None`).
 
 - How does it work: `low_cost_partial_config` if configured, will be used as an initial point of the search. It also affects the search trajectory. For more details about how does it play a role in the search algorithms, please refer to the papers about the search algorithms used: Section 2 of [Frugal Optimization for Cost-related Hyperparameters (CFO)](https://arxiv.org/pdf/2005.01571.pdf) and Section 3 of [Economical Hyperparameter Optimization with Blended Search Strategy (BlendSearch)](https://openreview.net/pdf?id=VbLH04pRA3).