def METHOD_NAME(filename):
    """Read events that are annotated during BITalino signal acquisition.
    Returns a dictionary containing the start and stop times (in seconds) in each channel detected
    per unique event (label) within each device."""
    file = filename.replace(".txt", "_EventsAnnotation.txt")
    if os.path.isfile(file) is False:
        return None
    with open(file, "r") as f:
        lines = f.readlines()
        if "OpenSignals" not in lines[0]:
            raise ValueError("Text file is not in OpenSignals format.")
        metadata = json.loads(lines[1][1:])  # read second line + skip '#'
        data = pd.read_csv(file, sep="\t", header=None, comment="#")
        data = data.dropna(axis=1, how="all")
        data.columns = metadata["columns"]["labels"]
    return {k: data[data["MAC"] == k] for k in data["MAC"].unique()}