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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 approle_token(vault_client, role_id, secret_id):
 """Returns a vault token based on the role and seret id"""

    resp = vault_client.auth_approle(role_id, secret_id)
    if 'auth' in resp and 'client_token' in resp['auth']:
        return resp['auth']['client_token']
    else:
        raise aomi.exceptions.AomiCredentials('invalid approle')