Using array type in Postgres with SQLAlchemy

I am using Postgres DB with SQLAlchemy as toolkit.

My model looks like

class Test(db.Model):

    """Test entry in DB."""
    __tablename__ = 'test'

    key1 = db.Column(db.String, primary_key=True)
    key2 = db.Column(postgresql.ARRAY(JSON))

I want to know how can I add elements to my key2 column which is an array?

For making changes to the DB, let's say I am using something of this kind:

test = Test(key1="key2", key2=array)

db.session.add(test)

How can I add new elements to this array or make a new array and assign it to key2? Basically struggling with proper documentation for JSON Arrays in Postgres/SQLAlchemy.

Any help would be highly appreciated.