'List all nodes.
:keyword location: Location (region) used as filter
:type    location: :class:`NodeLocation`
:return: List of node objects
:rtype: ``list`` of :class:`Node`'

def list_nodes(self, location=None):

    action = self._get_project_action('instance')
    data = {}
    if location:
        data['region'] = location.id
    response = self.connection.request(action, data=data)
    return self._to_nodes(response.object)
