'Constructor for Storage.
Args:
session: An instance of :class:`sqlalchemy.orm.Session`.
model_class: SQLAlchemy declarative mapping.
key_name: string, key name for the entity that has the credentials
key_value: key value for the entity that has the credentials
property_name: A string indicating which property on the
``model_class`` to store the credentials.
This property must be a
:class:`CredentialsType` column.'

def __init__(self, session, model_class, key_name, key_value, property_name):

    super(Storage, self).__init__()
    self.session = session
    self.model_class = model_class
    self.key_name = key_name
    self.key_value = key_value
    self.property_name = property_name
