How to get an output parameter value using sqlalchemy for a cx_Oracle stored procedure

Question

I have the following query in which the final parameter (var_clob) is an output parameter.

query = """
    BEGIN
    p_post_grade(
    :pin_term,
    :pin_crn,
    :pin_student_id,
    :pin_instructor_id,
    :pin_grade,
    :pin_grde_code_incmp_final,
    :pin_incomplete_ext_date,
    :var_clob);
COMMIT;
END;
"""

I store the parameters in a dictionary:

params = {
    "pin_term": json_body["term_code"],
    "pin_crn": json_body["section_id"],
    "pin_student_id": student["student_id"],
    "pin_instructor_id": json_body["instructor_id"],
    "pin_grade": student["grade"],
    "pin_grde_code_incmp_final": None,
    "pin_incomplete_ext_date": None
    "var_clob": sqlalchemy.sql.outparam("var_clob", type_=String)
 }

Then I call the sqlalchemy code to run the query

db_engine = create_engine('oracle+cx_oracle://' + db_username + ':' + db_pw + '@' + db_host + ':' +    db_port + '/' + db_name, echo='debug')

conn = db_engine.connect()
result = conn.execute(text(query), **params)

I end up getting the following error:

(cx_Oracle.NotSupportedError) Python value of type BindParameter not supported.

How do I properly get output parameter values in sqlalchemy for cx_Oracle?