fix isnull typo and formatting

docs/api/query-set/clause.md

@@ -1,6 +1,115 @@
 <a name="queryset.clause"></a>
 # queryset.clause
 
+<a name="queryset.clause.FilterGroup"></a>
+## FilterGroup Objects
+
+```python
+class FilterGroup()
+```
+
+Filter groups are used in complex queries condition to group and and or
+clauses in where condition
+
+<a name="queryset.clause.FilterGroup.resolve"></a>
+#### resolve
+
+```python
+ | resolve(model_cls: Type["Model"], select_related: List = None, filter_clauses: List = None) -> Tuple[List[FilterAction], List[str]]
+```
+
+Resolves the FilterGroups actions to use proper target model, replace
+complex relation prefixes if needed and nested groups also resolved.
+
+**Arguments**:
+
+- `model_cls (Type["Model"])`: model from which the query is run
+- `select_related (List[str])`: list of models to join
+- `filter_clauses (List[FilterAction])`: list of filter conditions
+
+**Returns**:
+
+`(Tuple[List[FilterAction], List[str]])`: list of filter conditions and select_related list
+
+<a name="queryset.clause.FilterGroup._iter"></a>
+#### \_iter
+
+```python
+ | _iter() -> Generator
+```
+
+Iterates all actions in a tree
+
+**Returns**:
+
+`(Generator)`: generator yielding from own actions and nested groups
+
+<a name="queryset.clause.FilterGroup._get_text_clauses"></a>
+#### \_get\_text\_clauses
+
+```python
+ | _get_text_clauses() -> List[sqlalchemy.sql.expression.TextClause]
+```
+
+Helper to return list of text queries from actions and nested groups
+
+**Returns**:
+
+`(List[sqlalchemy.sql.elements.TextClause])`: list of text queries from actions and nested groups
+
+<a name="queryset.clause.FilterGroup.get_text_clause"></a>
+#### get\_text\_clause
+
+```python
+ | get_text_clause() -> sqlalchemy.sql.expression.TextClause
+```
+
+Returns all own actions and nested groups conditions compiled and joined
+inside parentheses.
+Escapes characters if it's required.
+Substitutes values of the models if value is a ormar Model with its pk value.
+Compiles the clause.
+
+**Returns**:
+
+`(sqlalchemy.sql.elements.TextClause)`: complied and escaped clause
+
+<a name="queryset.clause.or_"></a>
+#### or\_
+
+```python
+or_(*args: FilterGroup, **kwargs: Any) -> FilterGroup
+```
+
+Construct or filter from nested groups and keyword arguments
+
+**Arguments**:
+
+- `args (Tuple[FilterGroup])`: nested filter groups
+- `kwargs (Any)`: fields names and proper value types
+
+**Returns**:
+
+`(ormar.queryset.clause.FilterGroup)`: FilterGroup ready to be resolved
+
+<a name="queryset.clause.and_"></a>
+#### and\_
+
+```python
+and_(*args: FilterGroup, **kwargs: Any) -> FilterGroup
+```
+
+Construct and filter from nested groups and keyword arguments
+
+**Arguments**:
+
+- `args (Tuple[FilterGroup])`: nested filter groups
+- `kwargs (Any)`: fields names and proper value types
+
+**Returns**:
+
+`(ormar.queryset.clause.FilterGroup)`: FilterGroup ready to be resolved
+
 <a name="queryset.clause.QueryClause"></a>
 ## QueryClause Objects
 
@@ -14,7 +123,7 @@ Constructs FilterActions from strings passed as arguments
 #### prepare\_filter
 
 ```python
- | prepare_filter(**kwargs: Any) -> Tuple[List[FilterAction], List[str]]
+ | prepare_filter(_own_only: bool = False, **kwargs: Any) -> Tuple[List[FilterAction], List[str]]
 ```
 
 Main external access point that processes the clauses into sqlalchemy text
@@ -23,6 +132,7 @@ mentioned in select_related strings but not included in select_related.
 
 **Arguments**:
 
+- `_own_only ()`: 
 - `kwargs (Any)`: key, value pair with column names and values
 
 **Returns**:
@@ -33,7 +143,7 @@ mentioned in select_related strings but not included in select_related.
 #### \_populate\_filter\_clauses
 
 ```python
- | _populate_filter_clauses(**kwargs: Any) -> Tuple[List[FilterAction], List[str]]
+ | _populate_filter_clauses(_own_only: bool, **kwargs: Any) -> Tuple[List[FilterAction], List[str]]
 ```
 
 Iterates all clauses and extracts used operator and field from related
@@ -104,3 +214,16 @@ present in alias_manager.
 
 `(List[FilterAction])`: list of actions with aliases changed if needed
 
+<a name="queryset.clause.QueryClause._verify_prefix_and_switch"></a>
+#### \_verify\_prefix\_and\_switch
+
+```python
+ | _verify_prefix_and_switch(action: "FilterAction") -> None
+```
+
+Helper to switch prefix to complex relation one if required
+
+**Arguments**:
+
+- `action (ormar.queryset.actions.filter_action.FilterAction)`: action to switch prefix in
+