update the dosc with split of queries, fix tests

docs/queries/aggregations.md

@@ -1,9 +1,16 @@
 # Aggregation functions
 
-`ormar` currently supports 2 aggregation functions:
+Currently 2 aggregation functions are supported.
 
-*  `count() -> int`
-*  `exists() -> bool`
+
+* `count() -> int`
+* `exists() -> bool`
+
+
+* `QuerysetProxy`
+    * `QuerysetProxy.count()` method
+    * `QuerysetProxy.exists()` method
+  
 
 ## count
 
@@ -11,6 +18,23 @@
 
 Returns number of rows matching the given criteria (i.e. applied with `filter` and `exclude`)
 
+```python
+class Book(ormar.Model):
+    class Meta:
+        tablename = "books"
+        metadata = metadata
+        database = database
+
+    id: int = ormar.Integer(primary_key=True)
+    title: str = ormar.String(max_length=200)
+    author: str = ormar.String(max_length=100)
+    genre: str = ormar.String(
+        max_length=100,
+        default="Fiction",
+        choices=["Fiction", "Adventure", "Historic", "Fantasy"],
+    )
+```
+
 ```python
 # returns count of rows in db for Books model
 no_of_books = await Book.objects.count()
@@ -22,7 +46,49 @@ no_of_books = await Book.objects.count()
 
 Returns a bool value to confirm if there are rows matching the given criteria (applied with `filter` and `exclude`)
 
+```python
+class Book(ormar.Model):
+    class Meta:
+        tablename = "books"
+        metadata = metadata
+        database = database
+
+    id: int = ormar.Integer(primary_key=True)
+    title: str = ormar.String(max_length=200)
+    author: str = ormar.String(max_length=100)
+    genre: str = ormar.String(
+        max_length=100,
+        default="Fiction",
+        choices=["Fiction", "Adventure", "Historic", "Fantasy"],
+    )
+```
+
 ```python
 # returns a boolean value if given row exists
 has_sample = await Book.objects.filter(title='Sample').exists()
 ```
+
+## QuerysetProxy methods
+
+When access directly the related `ManyToMany` field as well as `ReverseForeignKey`
+returns the list of related models.
+
+But at the same time it exposes a subset of QuerySet API, so you can filter, create,
+select related etc related models directly from parent model.
+
+### count
+
+Works exactly the same as [count](./#count) function above but allows you to select columns from related
+objects from other side of the relation.
+
+!!!tip 
+    To read more about `QuerysetProxy` visit [querysetproxy][querysetproxy] section
+
+### exists
+
+Works exactly the same as [exists](./#exists) function above but allows you to select columns from related
+objects from other side of the relation.
+
+!!!tip 
+    To read more about `QuerysetProxy` visit [querysetproxy][querysetproxy] section
+