The foreign key associated with column 'x.y' could not ... generate a foreign key to target column 'None'

I am during creating my first database project in SQLAlchemy and SQLite. I want to connect two entity as relational database's relational model. Here is the source:

class Models(Base):
   __tablename__ = "models"

   id_model = Column(Integer, primary_key=True)
   name_of_model = Column(String, nullable = False)
   price = Column(Integer, nullable = False)

   def __init__(self, name_of_model):
      self.name_of_model = name_of_model

class Cars(Base):

   __tablename__ = "cars"

   id_car = Column(Integer, primary_key=True)
   id_equipment = Column(Integer, nullable = False)  
   id_package = Column(Integer, nullable = False)

   id_model = Column(Integer, ForeignKey('Models'))
   model = relationship("Models", backref=backref('cars', order_by=id))

I want to achieve a relationship like this: https://imgur.com/af62zli

The error which occurs is:

The foreign key associated with column 'cars.id_model' could not find table 'Models' with which to generate a foreign key to target column 'None'.

Any ideas how to solve this problem?

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