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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def import_keypair(kwargs=None, call=None):
    '''
    Import an SSH public key.

    .. versionadded:: 2015.8.3
    '''
    if call != 'function':
        log.error(
            'The import_keypair function must be called with -f or --function.'
        )
        return False

    if not kwargs:
        kwargs = {}

    if 'keyname' not in kwargs:
        log.error('A keyname is required.')
        return False

    if 'file' not in kwargs:
        log.error('A public key file is required.')
        return False

    params = {'Action': 'ImportKeyPair',
              'KeyName': kwargs['keyname']}

    public_key_file = kwargs['file']

    if os.path.exists(public_key_file):
        with salt.utils.files.fopen(public_key_file, 'r') as fh_:
            public_key = salt.utils.stringutils.to_unicode(fh_.read())

    if public_key is not None:
        params['PublicKeyMaterial'] = base64.b64encode(public_key)

    data = aws.query(params,
                     return_url=True,
                     location=get_location(),
                     provider=get_provider(),
                     opts=__opts__,
                     sigver='4')
    return data