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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def initialise_shopify_session():
 """ Initialise the Shopify session with the Shopify App's API credentials. """

    if not settings.SHOPIFY_APP_API_KEY or not settings.SHOPIFY_APP_API_SECRET:
        raise ImproperlyConfigured("SHOPIFY_APP_API_KEY and SHOPIFY_APP_API_SECRET must be set in settings")
    shopify.Session.setup(api_key=settings.SHOPIFY_APP_API_KEY, secret=settings.SHOPIFY_APP_API_SECRET)