'Describes the permissions for a specified stack.
**Required Permissions**: To use this action, an IAM user must
have a Manage permissions level for the stack, or an attached
policy that explicitly grants permissions. For more
information on user permissions, see `Managing User
Permissions`_.
:type iam_user_arn: string
:param iam_user_arn: The user\'s IAM ARN. For more information about IAM
ARNs, see `Using Identifiers`_.
:type stack_id: string
:param stack_id: The stack ID.'

def describe_permissions(self, iam_user_arn=None, stack_id=None):

    params = {}
    if (iam_user_arn is not None):
        params['IamUserArn'] = iam_user_arn
    if (stack_id is not None):
        params['StackId'] = stack_id
    return self.make_request(action='DescribePermissions', body=json.dumps(params))
