Return a list of the BareMetal servers that are on the provider.

def list_nodes(call=None):
    ''' Return a list of the BareMetal servers that are on the provider.
    '''
    if call == 'action':
        raise SaltCloudSystemExit(
            'The list_nodes function must be called with -f or --function.'
        )

    items = query(method='servers')

    ret = {}
    for node in items['servers']:
        public_ips = []
        private_ips = []
        image_id = ''

        if node.get('public_ip'):
            public_ips = [node['public_ip']['address']]

        if node.get('private_ip'):
            private_ips = [node['private_ip']]

        if node.get('image'):
            image_id = node['image']['id']

        ret[node['name']] = {
            'id': node['id'],
            'image_id': image_id,
            'public_ips': public_ips,
            'private_ips': private_ips,
            'size': node['volumes']['0']['size'],
            'state': node['state'],
        }
    return ret