import json


def create_metadata_string(metadata):
    """
    Create a serialized json string from the given metadata.

    :param metadata: The metadata which should be serialized.
    :type metadata: MetadataContainer
    :return: Returns the string containing the json-style metadata
    :rtype: str
    """
    top_level_object = {"timestamp": metadata.timestamp}
    json_string = json.dumps(top_level_object)
    return json_string