<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def present(name, cidr_block, instance_tenancy=None, dns_support=None,
            dns_hostnames=None, tags=None, region=None, key=None, keyid=None,
            profile=None):
    '''
    Ensure VPC exists.

    name
        Name of the VPC.

    cidr_block
        The range of IPs in CIDR format, for example: 10.0.0.0/24. Block
        size must be between /16 and /28 netmask.

    instance_tenancy
        Instances launched in this VPC will be ingle-tenant or dedicated
        hardware.

    dns_support
        Indicates whether the DNS resolution is supported for the VPC.

    dns_hostnames
        Indicates whether the instances launched in the VPC get DNS hostnames.

    tags
        A list of tags.

    region
        Region to connect to.

    key
        Secret key to be used.

    keyid
        Access key to be used.

    profile
        A dict with region, key and keyid, or a pillar key (string) that
        contains a dict with region, key and keyid.
    '''
    ret = {'name': name,
           'result': True,
           'comment': '',
           'changes': {}
           }

    r = __salt__['boto_vpc.exists'](name=name, tags=tags, region=region,
                                    key=key, keyid=keyid, profile=profile)

    if 'error' in r:
        ret['result'] = False
        ret['comment'] = 'Failed to create VPC: {0}.'.format(r['error']['message'])
        return ret

    if not r.get('exists'):
        if __opts__['test']:
            ret['comment'] = 'VPC {0} is set to be created.'.format(name)
            ret['result'] = None
            return ret
        r = __salt__['boto_vpc.create'](cidr_block, instance_tenancy=instance_tenancy, vpc_name=name,
                                        enable_dns_support=dns_support, enable_dns_hostnames=dns_hostnames,
                                        tags=tags, region=region, key=key, keyid=keyid,
                                        profile=profile)
        if not r.get('created'):
            ret['result'] = False
            ret['comment'] = 'Error in creating VPC: {0}.'.format(r['error']['message'])
            return ret
        _describe = __salt__['boto_vpc.describe'](vpc_id=r['id'], region=region, key=key,
                                                  keyid=keyid, profile=profile)
        ret['changes']['old'] = {'vpc': None}
        ret['changes']['new'] = _describe
        ret['comment'] = 'VPC {0} created.'.format(name)
        return ret
    ret['comment'] = 'VPC present.'
    return ret