Connect to multiple data sources at once using Flask-GraphiQL

Question

I'm building a GraphQL API that connects to two different databases. I'm trying to create a GraphQL interface using Flask-GraphQL but it appears I can only bind a single SQLAlchemy session to the app at once via the context variable:

from flask import Flask
from flask_graphql import GraphQLView
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker, scoped_session
from schema import schema

# connect to database sources
engine1 = create_engine('sqlite:///db1.sqlite3')
engine2 = create_engine('sqlite:///db2.sqlite3')
session1 = scoped_session(sessionmaker(bind=engine1))
session2 = scoped_session(sessionmaker(bind=engine2))

# create app and add GraphiQL route
app = Flask(__name__)
app.add_url_rule('/graphql', view_func=GraphQLView.as_view(
    'graphql',
    schema=schema,
    graphiql=True,
    get_context=lambda: {'session': session1}
))

Is there any way to connect to more than one data source at once or is this not possible?