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

def nat_gateway_exists(nat_gateway_id=None, subnet_id=None, subnet_name=None,
                       vpc_id=None, vpc_name=None,
                       states=('pending', 'available'),
                       region=None, key=None, keyid=None, profile=None):
    '''
    Checks if a nat gateway exists.

    This function requires boto3 to be installed.

    .. versionadded:: 2016.11.0

    CLI Example:

    .. code-block:: bash

        salt myminion boto_vpc.nat_gateway_exists nat_gateway_id='nat-03b02643b43216fe7'
        salt myminion boto_vpc.nat_gateway_exists subnet_id='subnet-5b05942d'

    '''

    return bool(_find_nat_gateways(nat_gateway_id=nat_gateway_id,
                                   subnet_id=subnet_id,
                                   subnet_name=subnet_name,
                                   vpc_id=vpc_id,
                                   vpc_name=vpc_name,
                                   states=states,
                           region=region, key=key, keyid=keyid,
                           profile=profile))