title: SQLAlchemy only loads collection, not backref when eagerloading
body: <p>For example (eagerload/joinedload do the same thing):</p>
  
  <pre><code>session = Session()    
  parents = session.query(Parent).options(joinedload(Parent.children)).all()
  session.close()
  
  print parents[0].children  # This works
  print parents[0].children[0].parent  # This gives a lazy loading error
  </code></pre>
  
  <p>Adding the following loop before closing the session works (and doesn't hit the DB):</p>
  
  <pre><code>for p in parents:
    for c in p.children:
      c.parent
  </code></pre>
  
  <p>Which is pretty dumb. Is there a way to alter the original query so that it loads both sides of the relation without adding more joins in the output SQL?</p>
  
  <p><strong>update</strong> In case it's relevant; here's the mapping</p>
  
  <pre><code>class Parent(Entity):
    __tablename__ = "parent"
  
    id = Column(Integer, primary_key=True)
    children = relation("Child", backref="parent")
  
  class Child(Entity):
    __tablename__ = "child"
  
    id = Column(Integer, primary_key=True)
    parentId = Column(Integer, ForeignKey("parent.id"), index=True)
  </code></pre>