'Return the public SSH key for the resource.'

@property
def public_key(self):

    if (not self._public_key):
        if self.properties[self.PUBLIC_KEY]:
            self._public_key = self.properties[self.PUBLIC_KEY]
        elif self.resource_id:
            nova_key = self.client_plugin().get_keypair(self.resource_id)
            self._public_key = nova_key.public_key
    return self._public_key
