'Update a volume_type extra spec.
volume_type_id: Id of volume_type.
extra_spec_name: Name of the extra spec to be updated.
extra_spec: A dictionary of with key as extra_spec_name and the
updated value.
For a full list of available parameters, please refer to the official
API reference:
http://developer.openstack.org/api-ref/block-storage/v1/#update-extra-specs-for-a-volume-type-v1'

def update_volume_type_extra_specs(self, volume_type_id, extra_spec_name, extra_specs):

    url = ('types/%s/extra_specs/%s' % (volume_type_id, extra_spec_name))
    put_body = json.dumps(extra_specs)
    (resp, body) = self.put(url, put_body)
    body = json.loads(body)
    self.expected_success(200, resp.status)
    return rest_client.ResponseBody(resp, body)
