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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 get_default_connection_details():
 """ Gets the connection details based on environment vars or Thanatos default settings. :return: Returns a dictionary of connection details. :rtype: dict """


    return {
        'host': os.environ.get('MYSQL_HOST', '127.0.0.1'),
        'user': os.environ.get('MYSQL_USER', 'vagrant'),
        'password': os.environ.get('MYSQL_PASSWORD', 'vagrant'),
        'database': os.environ.get('MYSQL_DB', 'thanatos'),
    }