>>> select([t], t.c.object['object_id']=='x')
<sqlalchemy.sql.selectable.Select object at 0x7f120baf18d0>

>>> conn.execute(select([t], t.c.object['object_id']=='x'))
Traceback (most recent call last):
  File "/home/jim/.pyenv/versions/3.6.13/lib/python3.6/site-packages/sqlalchemy/sql/compiler.py", line 2071, in visit_binary
    opstring = OPERATORS[operator_]
KeyError: <function json_getitem_op at 0x7f120bfa9d08>

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
...
  File "/home/jim/.pyenv/versions/3.6.13/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 207, in raise_
    raise exception
sqlalchemy.exc.UnsupportedCompilationError: Compiler <pybigquery.sqlalchemy_bigquery.BigQueryCompiler object at 0x7f120baf1a20> can't render element of type <function json_getitem_op at 0x7f120bfa9d08> (Background on this error at: https://sqlalche.me/e/14/l7de)