add example of the variation of remove method

docs/reference/models.md

@@ -490,7 +490,7 @@ Use the `all` method to find lots of items. Pass it a set of query parameters in
 - `query [object]`: if the query is an object, it will be interpreted as a Query object
 
 ##### options
-- `sort [object]`: each key is a property name, each value can either be `asc` or `desc`. 
+- `sort [object]`: each key is a property name, each value can either be `asc` or `desc`.
 - `includes [array]`: Using SQL adapters, you may supply an array of model association names to eager-load.
 
 ##### example
@@ -527,6 +527,20 @@ User.remove('abc-123', function (err, data) {
 });
 ```
 
+`remove(condition, fn)`
+
+Remove instances from the database by condition
+
+##### condition
+- `condition [object]`: the key value condition of instances to be removed
+
+##### examples
+```
+User.remove({state: "inactive"}, function (err, data) {
+  // do something now that it's removed.
+});
+```
+
 * * *
 
 #### queries