Deletes the specified policy document for the specified group.

        :type group_name: string
        :param group_name: The name of the group the policy is associated with.

        :type policy_name: string
        :param policy_name: The policy document to delete.

def delete_group_policy(self, group_name, policy_name):
        """
        Deletes the specified policy document for the specified group.

        :type group_name: string
        :param group_name: The name of the group the policy is associated with.

        :type policy_name: string
        :param policy_name: The policy document to delete.
        
        """
        params = {'GroupName' : group_name,
                  'PolicyName' : policy_name}
        return self.get_response('DeleteGroupPolicy', params, verb='POST')