Given a list of checked operations, find the ones that collide.
        Return a dict structured as history_id_key --> [history_id]

def find_collisions( self, checked_ops ):
        """
        Given a list of checked operations, find the ones that collide.
        Return a dict structured as history_id_key --> [history_id]
        """

        collisions = {}
        for op in checked_ops:
            if BlockstackDB.nameop_is_collided( op ):
                BlockstackDB.nameop_put_collision( collisions, op )

        return collisions