def calculate_enrichment(coverage_values):
    """Calculate TSS enrichment value for a dataset

    Parameters
    ----------
    coverage_values
        iterable of tuples (tss_center_depth, flank_depth) per TSS
    
    Returns
    -------
    float
        the TSS enrichment value
    """

    tss_depth, flank_depth = (sum(z) for z in zip(*coverage_values))
    return tss_depth / flank_depth