'Unassigns an assigned Amazon EBS volume. The volume remains
registered with the stack. For more information, see `Resource
Management`_.
**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 volume_id: string
:param volume_id: The volume ID.'

def unassign_volume(self, volume_id):

    params = {'VolumeId': volume_id}
    return self.make_request(action='UnassignVolume', body=json.dumps(params))
