def plot_counts(axis, data):
    """
    plots APD timeseries data

    Args:
        axis: the axis to draw the plot
        data (2d array): APD count timeseries data

    Returns: (none)
    """
    axis.plot(data, linewidth=2.0)
    axis.set_xlabel('time')
    axis.set_ylabel('kCounts/sec')
