sqlalchemy.py

class Foo (Base):
  a = Column(Integer, ForeignKey='sometable.id', primary_key = True)
  b = Column(Integer, ForeignKey='other_table.id', primary_key = True)
  c = ...
  
Class Boo (Base):
  id = Column(Integer, primary_key = True)
  ....
  
// Association table for many to many relationship between A and B
Class A_Link_B(Base):
  boo_id = Column(Integer, ForeignKey='Boo.id', primary_key = True)
  fod_id = composite of primary keys in Foo table as a FK here 
  ...