Assigns a Floating IP to a Droplet.

def assign_floating_ip(self, ip_addr, droplet_id):
        """
        Assigns a Floating IP to a Droplet.
        """
        if self.api_version == 2:
            params = {'type': 'assign','droplet_id': droplet_id}

            json = self.request('/floating_ips/' + ip_addr + '/actions', params=params, method='POST')
            return json['action']
        else:
            raise DoError(v2_api_required_str)