update docs part 1

docs_src/models/docs004.py

@@ -8,14 +8,16 @@ metadata = sqlalchemy.MetaData()
 
 
 class Course(ormar.Model):
-    __database__ = database
-    __metadata__ = metadata
+    class Meta:
+        database = database
+        metadata = metadata
 
-    id = ormar.Integer(primary_key=True)
-    name = ormar.String(length=100)
-    completed = ormar.Boolean(default=False)
+    id: ormar.Integer(primary_key=True)
+    name: ormar.String(max_length=100)
+    completed: ormar.Boolean(default=False)
 
-print(Course.__table__.columns)
+
+print(Course.Meta.table.columns)
 """
 Will produce:
 ['courses.id', 'courses.name', 'courses.completed']