Query for tables with relationships

I’ve created two tables named question and category.

questions = Table(
“questions”,
metadata,
Column(“id”, Integer, primary_key=True),
Column(“title”, String(50)),
Column(“category_id”, Integer, ForeignKey(“categories.id”)),
)
categories = Table(
“categories”,
metadata,
Column(“id”, Integer, primary_key=True),
Column(“title”, String(50)),
)

I’m doing the simple queries using this doc, but I couldn’t figure out how to do a joined query (eg: getting all questions of category_x). I have no idea if I defined the tabes correctly and how to query these tables.