Maximum recursion depth, when using relations about restfulpy HOT 2 CLOSED

from sqlalchemy import Column, String, Integer, create_engine, ForeignKey, MetaData
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import Session
from restfulpy.orm import BaseModel, relationship
metadata = MetaData()
Base = declarative_base(cls=BaseModel, metadata=metadata)


class Employee(Base):
    __tablename__ = 'employee'
    id = Column(Integer, primary_key=True)
    name = Column(String(50))
    type = Column(String(20))
    images = relationship('Image', secondary='image_relations', back_populates='employee')


class Image(Base):
    __tablename__ = 'images'
    id = Column(Integer, primary_key=True)
    src = Column(String(100))
    employee = relationship('Employee', secondary='image_relations', back_populates='images', protected=True)


class ImageRelation(Base):
    __tablename__ = 'image_relations'
    employee_id = Column(Integer, ForeignKey('employee.id'), primary_key=True)
    image_id = Column(Integer, ForeignKey('images.id'), primary_key=True)


engine = create_engine('sqlite://', echo=True)
Base.metadata.create_all(engine)
session = Session(engine, autoflush=False, autocommit=False, expire_on_commit=True)


@Employee.expose
def run():
    emp1 = Employee()
    emp1.id = 1
    emp1.name = 'dia gram'
    emp1.images.append(Image(src='lorem.com'))
    session.add(emp1)
    session.commit()
    return emp1


print(run().to_dict())