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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 _plaintext_data_key():
    '''
    Return the configured KMS data key decrypted and encoded in urlsafe base64.

    Cache the result to minimize API calls to AWS.
    '''
    response = getattr(_plaintext_data_key, 'response', None)
    cache_hit = response is not None
    if not cache_hit:
        response = _api_decrypt()
        setattr(_plaintext_data_key, 'response', response)
    key_id = response['KeyId']
    plaintext = response['Plaintext']
    if hasattr(plaintext, 'encode'):
        plaintext = plaintext.encode(__salt_system_encoding__)
    log.debug('Using key %s from %s', key_id, 'cache' if cache_hit else 'api call')
    return plaintext