How to select records containing given value in a JSON array in PostgreSQL JSON field using SQLAlchemy?

Question

I have items (users) in a PostgeSQL database with JSON data field with such structure:

{
  "department": [
    "IT"
  ],
  "competencies": [
    "moderator",
    "language_ru",
    "language_en"
  ]
}

Database is accessed using flask-sqlalchemy.

from sqlalchemy.dialects.postgresql import JSON

class UserDBO(db.Model):
    __tablename__ = 'user'
    id = db.Column(db.BigInteger, primary_key=True)
    display_name = db.Column(db.String(length=100), index=True),
    email = db.Column(db.String(length=254), index=True)
    phone = db.Column(db.String(length=16), index=True)
    created = db.Column(db.DateTime)
    data = db.Column(JSON, default={}, nullable=False)

I need to select users that have certain competencies. I had tried the following filters for sqlalchemy query (none worked as expected, most return errors):

from sqlalchemy.types import Unicode, String
from sqlalchemy import cast
from sqlalchemy import func
from sqlalchemy.dialects import postgresql
records = UserDBO.query.filter(
            # func.json_contains(UserDBO.data['competencies'],cast('moderator', String)),
            # UserDBO.data['competencies'].contains({'competencies':['moderator']}),
            # UserDBO.data['competencies'].contains('moderator')
            # UserDBO.data['competencies'].astext.cast(Unicode) == 'moderator',
            # UserDBO.data['competencies'] == ['moderator'],
            # ['moderator'] in UserDBO.data['competencies'],
            # ['moderator'] in UserDBO.data['competencies'],
            # UserDBO.data['competencies'] == cast('moderator', Unicode),
        )

I need to select items that match several competencies like ['moderator','language_en'] in UserDBO.data['competencies'].

Selecting them one by one using some filter like 'moderator' in UserDBO.data['competencies'] for one competency is also OK.

Also it will be very interesting to optimize such query by creating appropriate indeces.