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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 read_creds_from_environment_variables():
 """ Read credentials from environment variables :return: """

    creds = init_creds()
    # Check environment variables
    if 'AWS_ACCESS_KEY_ID' in os.environ and 'AWS_SECRET_ACCESS_KEY' in os.environ:
        creds['AccessKeyId'] = os.environ['AWS_ACCESS_KEY_ID']
        creds['SecretAccessKey'] = os.environ['AWS_SECRET_ACCESS_KEY']
        if 'AWS_SESSION_TOKEN' in os.environ:
            creds['SessionToken'] = os.environ['AWS_SESSION_TOKEN']
    return creds