diff --git a/src/orm2pydantic/sqla.py b/src/orm2pydantic/sqla.py
index 06d96d8..12e7feb 100644
--- a/src/orm2pydantic/sqla.py
+++ b/src/orm2pydantic/sqla.py
@@ -13,6 +13,7 @@ from .utils import resolve_dotted_path
 
 __all__ = [
     'field_from_column',
+    'field_from_relationship',
     'from_sqla'
 ]
 
@@ -27,7 +28,9 @@ class OrmConfig(BaseConfig):
     orm_mode = True
 
 
-def field_from_column(column: Column) -> FieldDef:
+def field_from_column(col_prop: ColumnProperty) -> FieldDef:
+    assert len(col_prop.columns) == 1
+    column: Column = col_prop.columns[0]
     try:
         field_type = column.type.impl.python_type
     except AttributeError:
@@ -50,26 +53,26 @@ def field_from_column(column: Column) -> FieldDef:
     return field_type, field_info
 
 
-def from_sqla(db_model: Type[DeclarativeMeta], incl_many_to_one: bool = True, incl_one_to_many: bool = False,
-              config: Type[BaseConfig] = OrmConfig, exclude: Container[str] = (),
-              add_fields: dict[str, FieldDef] = None):
+def field_from_relationship(rel_prop: RelationshipProperty) -> FieldDef:
+    assert isinstance(rel_prop.mapper, Mapper)
+    if rel_prop.direction.name == 'MANYTOONE':
+        return rel_prop.mapper.class_.__name__, Field(default=None)
+    if rel_prop.direction.name == 'ONETOMANY':
+        return list[rel_prop.mapper.class_.__name__], Field(default=None)
+
+
+def from_sqla(db_model: Type[DeclarativeMeta], config: Type[BaseConfig] = OrmConfig, exclude: Container[str] = (),
+              incl_relationships: bool = True, add_fields: dict[str, FieldDef] = None):
     assert isinstance(db_model, DeclarativeMeta)
-    assert not (incl_one_to_many and incl_many_to_one), "Pydantic is unable to handle the circular relationship"
     fields = {}
     for attr in inspect(db_model).attrs:
         if attr.key in exclude:
             continue
         if isinstance(attr, ColumnProperty):
-            assert len(attr.columns) == 1
-            column = attr.columns[0]
-            fields[attr.key] = field_from_column(column)
+            fields[attr.key] = field_from_column(attr)
         elif isinstance(attr, RelationshipProperty):
-            related = attr.mapper
-            assert isinstance(related, Mapper)
-            if incl_many_to_one and attr.direction.name == 'MANYTOONE':
-                fields[attr.key] = (related.class_.__name__, Field(default=None))
-            if incl_one_to_many and attr.direction.name == 'ONETOMANY':
-                fields[attr.key] = (list[related.class_.__name__], Field(default=None))
+            if incl_relationships:
+                fields[attr.key] = field_from_relationship(attr)
         else:
             raise AssertionError("Unknown attr type", attr)
     if add_fields is not None:
diff --git a/tests/informal.py b/tests/informal.py
index 641762d..dabdd14 100644
--- a/tests/informal.py
+++ b/tests/informal.py
@@ -17,8 +17,6 @@ def default_factory() -> str: return '1'
 class AbstractBase(ORMBase):
     __abstract__ = True
 
-    NON_REPR_FIELDS = ['id', 'date_created', 'date_updated']
-
     date_created = Column(TIMESTAMP(timezone=False), server_default=db_now())
     date_updated = Column(TIMESTAMP(timezone=False), server_default=db_now(), onupdate=db_now())
 
@@ -37,7 +35,7 @@ class City(AbstractBase):
     __tablename__ = 'city'
 
     id = Column(Integer, primary_key=True)
-    state_province_id = Column(Integer, FKey('state_province.id', ondelete='RESTRICT'), index=True)
+    state_province_id = Column(Integer, FKey('state_province.id', ondelete='RESTRICT'), nullable=False, index=True)
     zip_code = Column(String(5), nullable=False, index=True)
     name = Column(Unicode(255), nullable=False, index=True)
 
@@ -48,7 +46,7 @@ class Street(AbstractBase):
     __tablename__ = 'street'
 
     id = Column(Integer, primary_key=True)
-    city_id = Column(Integer, FKey('city.id', ondelete='RESTRICT'), index=True)
+    city_id = Column(Integer, FKey('city.id', ondelete='RESTRICT'), nullable=False, index=True)
     name = Column(Unicode(255), nullable=False, index=True)
 
     addresses = relationship('Address', backref='street', lazy='selectin')
@@ -58,7 +56,7 @@ class Address(AbstractBase):
     __tablename__ = 'address'
 
     id = Column(Integer, primary_key=True)
-    street_id = Column(Integer, FKey('street.id', ondelete='RESTRICT'), index=True)
+    street_id = Column(Integer, FKey('street.id', ondelete='RESTRICT'), nullable=False, index=True)
     house_number = Column(String(8), nullable=False, default=default_factory)
     supplement = Column(String(255))
 
@@ -67,9 +65,9 @@ def main_test() -> None:
     engine = create_engine("sqlite://")
     AbstractBase.metadata.create_all(engine)
 
-    _PydanticStateProvince = from_sqla(StateProvince)
-    _PydanticCity = from_sqla(City)
-    _PydanticStreet = from_sqla(Street)
+    _PydanticStateProvince = from_sqla(StateProvince, exclude=['cities'])
+    _PydanticCity = from_sqla(City, exclude=['streets'])
+    _PydanticStreet = from_sqla(Street, exclude=['addresses'])
     _PydanticAddress = from_sqla(Address)
 
     with Session(engine) as session: