Checks to see if a session currently exists in DynamoDB.

        :rtype: bool
        :returns: ``True`` if a session with the given key exists in the DB,
            ``False`` if not.

def exists(self, session_key):
        """
        Checks to see if a session currently exists in DynamoDB.

        :rtype: bool
        :returns: ``True`` if a session with the given key exists in the DB,
            ``False`` if not.
        """

        response = self.table.get_item(
            Key={'session_key': session_key},
            ConsistentRead=ALWAYS_CONSISTENT)
        if 'Item' in response:
            return True
        else:
            return False