AWS RDS Proxy error (postgres) - RDS Proxy currently doesn’t support command-line options

I try to read or write from/to an AWS RDS Proxy with a postgres RDS as the endpoint. The operation works with psql but fails on the same client with pg8000 or psycopg2 as client libraries in Python.

The operation works with with pg8000 and psycopg2 if I use the RDS directly as endpoint (without the RDS proxy).

sqlaclchemy/psycopg2 error message:

Feature not supported: RDS Proxy currently doesn’t support command-line options.

A minimal version of the code I use:

from sqlalchemy import create_engine

import os
from dotenv import load_dotenv
load_dotenv()

login_string = os.environ['login_string_proxy']
engine = create_engine(login_string, client_encoding="utf8", echo=True, connect_args={'options': '-csearch_path={}'.format("testing")})
engine.execute(f"INSERT INTO testing.mytable (product) VALUES ('123')")

pg8000: the place it stops / waits for something is in core.py:

def sock_read(b):
            try:
                return self._sock.read(b)
            except OSError as e:
                raise InterfaceError("network error on read") from e

A minimal version of the code I use:

import pg8000

import os
from dotenv import load_dotenv
load_dotenv()

db_connection = pg8000.connect(database=os.environ['database'], host=os.environ['host'], port=os.environ['port'], user=os.environ['user'], password=os.environ['password'])
db_connection.run(f"INSERT INTO mytable (data) VALUES ('data')")
db_connection.commit()
db_connection.close()

The logs in the RDS Proxy looks always normal for all the examples I mentioned - e.g.:

A new client connected from ...:60614.
Received Startup Message: [username="", database="", protocolMajorVersion=3, protocolMinorVersion=0, sslEnabled=false]
Proxy authentication with PostgreSQL native password authentication succeeded for user "" with TLS off.
A TCP connection was established from the proxy at ...:42795 to the database at ...:5432.
The new database connection successfully authenticated with TLS off.

I opened up all ports via security groups on the RDS and the RDS proxy and I used an EC2 inside the VPC.

I tried with autocommit on and off.