fix bug with infinite relation auto extraction, finish initial relations docs

orm/fields/base.py

@@ -35,7 +35,7 @@ class BaseField:
     @property
     def is_required(self) -> bool:
         return (
-                not self.nullable and not self.has_default and not self.is_auto_primary_key
+            not self.nullable and not self.has_default and not self.is_auto_primary_key
         )
 
     @property

orm/fields/foreign_key.py

@@ -25,12 +25,12 @@ def create_dummy_instance(fk: Type["Model"], pk: Any = None) -> "Model":
 
 class ForeignKey(BaseField):
     def __init__(
-            self,
-            to: Type["Model"],
-            name: str = None,
-            related_name: str = None,
-            nullable: bool = True,
-            virtual: bool = False,
+        self,
+        to: Type["Model"],
+        name: str = None,
+        related_name: str = None,
+        nullable: bool = True,
+        virtual: bool = False,
     ) -> None:
         super().__init__(nullable=nullable, name=name)
         self.virtual = virtual
@@ -50,7 +50,7 @@ class ForeignKey(BaseField):
         return to_column.get_column_type()
 
     def _extract_model_from_sequence(
-            self, value: List, child: "Model"
+        self, value: List, child: "Model"
     ) -> Union["Model", List["Model"]]:
         return [self.expand_relationship(val, child) for val in value]
 
@@ -76,10 +76,12 @@ class ForeignKey(BaseField):
 
     def register_relation(self, model: "Model", child: "Model") -> None:
         child_model_name = self.related_name or child.get_name()
-        model._orm_relationship_manager.add_relation(model, child, child_model_name, virtual=self.virtual)
+        model._orm_relationship_manager.add_relation(
+            model, child, child_model_name, virtual=self.virtual
+        )
 
     def expand_relationship(
-            self, value: Any, child: "Model"
+        self, value: Any, child: "Model"
     ) -> Optional[Union["Model", List["Model"]]]:
 
         if value is None: