'List sizes on a provider.
Abiquo does not work with sizes. However, this method
returns a list of predefined ones (copied from :class:`DummyNodeDriver`
but without price neither bandwidth) to help the users to create their
own.
If you call the method :class:`AbiquoNodeDriver.create_node` with the
size informed, it will just override the \'ram\' value of the \'image\'
template. So it is no too much usefull work with sizes...
:return: The list of sizes
:rtype:  ``list`` of :class:`NodeSizes`'

def list_sizes(self, location=None):

    return [NodeSize(id=1, name='Small', ram=128, disk=4, bandwidth=None, price=None, driver=self), NodeSize(id=2, name='Medium', ram=512, disk=16, bandwidth=None, price=None, driver=self), NodeSize(id=3, name='Big', ram=4096, disk=32, bandwidth=None, price=None, driver=self), NodeSize(id=4, name='XXL    Big', ram=(4096 * 2), disk=(32 * 4), bandwidth=None, price=None, driver=self)]
