SQL Alchemy relationships

Below, you can see a code that represents the connection between two tables: singers and their songs.

from sqlalchemy.orm import relationship


class Singer(Base):

    __tablename__ = "singer"

    id = Column(Integer, primary_key=True, autoincrement="auto")
    username = Column(String(255), unique=True, nullable=False)
    first_name = Column(String(255))
    last_name = Column(String(255))
    song_id = Column(Integer, ForeignKey("song.id"))
    song = relationship("Song")
    

class Song(Base):
 
    __tablename__ = "song"

    id = Column(Integer, primary_key=True, index=True)
    song_name = Column(String(255), nullable=False)
    
    

   

What type of relationship is this?

Pay attention to where relationship() is declared.