'Return list of sizes on a provider.
@inherits: :class:`NodeDriver.list_sizes`
:return: List of compute node sizes supported by the cloud provider.
:rtype:  ``list`` of :class:`OpenNebulaNodeSize`'

def list_sizes(self, location=None):

    return [NodeSize(id=1, name='small', ram=None, disk=None, bandwidth=None, price=None, driver=self), NodeSize(id=2, name='medium', ram=None, disk=None, bandwidth=None, price=None, driver=self), NodeSize(id=3, name='large', ram=None, disk=None, bandwidth=None, price=None, driver=self)]
