def _get_fields(events):
    """
    Returns a list of all fields in the given event set.

    @param events: The events as a list of dictionaries.
    @type events: list(dict(str: str))
    @return: All the fields.
    @rtype: set(str)
    """
    fields = set()
    for event in events:
        fields.update(list(event.keys()))
    return fields