def METHOD_NAME(self, instance_id, groups, dry_run=False):
    """
    Links  an EC2-Classic instance to a ClassicLink-enabled VPC through one
    or more of the VPC's security groups. You cannot link an EC2-Classic
    instance to more than one VPC at a time. You can only link an instance
    that's in the running state. An instance is automatically unlinked from
    a VPC when it's stopped. You can link it to the VPC again when you
    restart it.
    After you've linked an instance, you cannot  change  the VPC security
    groups  that are associated with it. To change the security groups, you
    must first unlink the instance, and then link it again.
    Linking your instance to a VPC is sometimes referred  to  as  attaching
    your instance.
    :type intance_id: str
    :param instance_is: The ID of a ClassicLink-enabled VPC.
    :tye groups: list
    :param groups: The ID of one or more of the VPC's security groups.
        You cannot specify security groups from a different VPC. The
        members of the list can be
        :class:`boto.ec2.securitygroup.SecurityGroup` objects or
        strings of the id's of the security groups.
    :type dry_run: bool
    :param dry_run: Set to True if the operation should not actually run.
    :rtype: bool
    :return: True if successful
    """
    return self.connection.attach_classic_link_vpc(
        vpc_id=self.id,
        instance_id=instance_id,
        groups=groups,
        dry_run=dry_run
    )