✨ Add source examples for docs

docs_src/tutorial/many_to_many/tutorial002.py

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+from typing import List, Optional
+
+from sqlmodel import Field, Relationship, Session, SQLModel, create_engine, select
+
+
+class HeroTeamLink(SQLModel, table=True):
+    team_id: Optional[int] = Field(
+        default=None, foreign_key="team.id", primary_key=True
+    )
+    hero_id: Optional[int] = Field(
+        default=None, foreign_key="hero.id", primary_key=True
+    )
+
+
+class Team(SQLModel, table=True):
+    id: Optional[int] = Field(default=None, primary_key=True)
+    name: str
+    headquarters: str
+
+    heroes: List["Hero"] = Relationship(back_populates="teams", link_model=HeroTeamLink)
+
+
+class Hero(SQLModel, table=True):
+    id: Optional[int] = Field(default=None, primary_key=True)
+    name: str
+    secret_name: str
+    age: Optional[int] = None
+
+    teams: List[Team] = Relationship(back_populates="heroes", link_model=HeroTeamLink)
+
+
+sqlite_file_name = "database.db"
+sqlite_url = f"sqlite:///{sqlite_file_name}"
+
+engine = create_engine(sqlite_url, echo=True)
+
+
+def create_db_and_tables():
+    SQLModel.metadata.create_all(engine)
+
+
+def create_heroes():
+    with Session(engine) as session:
+        team_preventers = Team(name="Preventers", headquarters="Sharp Tower")
+        team_z_force = Team(name="Z-Force", headquarters="Sister Margaret’s Bar")
+
+        hero_deadpond = Hero(
+            name="Deadpond",
+            secret_name="Dive Wilson",
+            teams=[team_z_force, team_preventers],
+        )
+        hero_rusty_man = Hero(
+            name="Rusty-Man",
+            secret_name="Tommy Sharp",
+            age=48,
+            teams=[team_preventers],
+        )
+        hero_spider_boy = Hero(
+            name="Spider-Boy", secret_name="Pedro Parqueador", teams=[team_preventers]
+        )
+        session.add(hero_deadpond)
+        session.add(hero_rusty_man)
+        session.add(hero_spider_boy)
+        session.commit()
+
+        session.refresh(hero_deadpond)
+        session.refresh(hero_rusty_man)
+        session.refresh(hero_spider_boy)
+
+        print("Deadpond:", hero_deadpond)
+        print("Deadpond teams:", hero_deadpond.teams)
+        print("Rusty-Man:", hero_rusty_man)
+        print("Rusty-Man Teams:", hero_rusty_man.teams)
+        print("Spider-Boy:", hero_spider_boy)
+        print("Spider-Boy Teams:", hero_spider_boy.teams)
+
+
+def update_heroes():
+    with Session(engine) as session:
+        hero_spider_boy = session.exec(
+            select(Hero).where(Hero.name == "Spider-Boy")
+        ).one()
+        team_z_force = session.exec(select(Team).where(Team.name == "Z-Force")).one()
+
+        team_z_force.heroes.append(hero_spider_boy)
+        session.add(team_z_force)
+        session.commit()
+
+        print("Updated Spider-Boy's Teams:", hero_spider_boy.teams)
+        print("Z-Force heroes:", team_z_force.heroes)
+
+        hero_spider_boy.teams.remove(team_z_force)
+        session.add(team_z_force)
+        session.commit()
+
+        print("Reverted Z-Force's heroes:", team_z_force.heroes)
+        print("Reverted Spider-Boy's teams:", hero_spider_boy.teams)
+
+
+def main():
+    create_db_and_tables()
+    create_heroes()
+    update_heroes()
+
+
+if __name__ == "__main__":
+    main()