'Lists all sizes
:return: A list of all configurable node sizes.
:rtype: ``list`` of :class:`NodeSize`'

def list_sizes(self):

    sizes = []
    fixed_instances = self._list_fixed_instances()
    for value in fixed_instances:
        node_size = self._to_node_size(value)
        sizes.append(node_size)
    return sizes
