'Adds an OS image that is currently stored in a storage account in your
subscription to the image repository.
label:
Specifies the friendly name of the image.
media_link:
Specifies the location of the blob in Windows Azure blob store
where the media for the image is located. The blob location must
belong to a storage account in the subscription specified by the
<subscription-id> value in the operation call. Example:
http://example.blob.core.windows.net/disks/mydisk.vhd
name:
Specifies a name for the OS image that Windows Azure uses to
identify the image when creating one or more virtual machines.
os:
The operating system type of the OS image. Possible values are:
Linux, Windows'

def add_os_image(self, label, media_link, name, os):

    _validate_not_none('label', label)
    _validate_not_none('media_link', media_link)
    _validate_not_none('name', name)
    _validate_not_none('os', os)
    return self._perform_post(self._get_image_path(), _XmlSerializer.os_image_to_xml(label, media_link, name, os), async=True)
