func (c *ec2MetadataClientImpl) VPCID(mac string) (string, error) {
	return c.client.GetMetadata(fmt.Sprintf(VPCIDResourceFormat, mac))
}
func (c *ec2MetadataClientImpl) VPCID(mac string) (string, error) {
	return c.client.GetMetadata(fmt.Sprintf(VPCIDResourceFormat, mac))
}
// VPCID returns the VPC id for the network interface, given
// its mac address