How to use the sparkpost.django.email_backend.SparkPostEmailBackend function in sparkpost

def test_default_base_uri_retrieval():
    backend = SparkPostEmailBackend()
    assert backend.client.base_uri.startswith('https://' + US_API)

def test_eu_base_uri_retrieval():
    reconfigure_settings(SPARKPOST_BASE_URI=EU_API)
    backend = SparkPostEmailBackend()
    assert backend.client.base_uri.startswith('https://' + EU_API)

def test_password_retrieval():
    backend = SparkPostEmailBackend()
    assert backend.client.api_key == API_KEY

def __init__(self, fail_silently=False, **kwargs):
        super(SparkPostEmailBackend, self)\
            .__init__(fail_silently=fail_silently, **kwargs)

        sp_api_key = getattr(settings, 'SPARKPOST_API_KEY', None)
        sp_base_uri = getattr(settings, 'SPARKPOST_BASE_URI', US_API)

        self.client = SparkPost(sp_api_key, sp_base_uri)