def get_length_w(fig_width, region_start, region_end, fontsize):
    """
    to improve the visualization of the labels
    it is good to have an estimation of their length
    in base pairs. In the following code I try to get the
    length of a 'W' in base pairs.
    """
    inches_per_pt = 1.0 / 72.27
    font_in_inches = fontsize * inches_per_pt
    region_len = region_end - region_start
    bp_per_inch = region_len / fig_width
    font_in_bp = font_in_inches * bp_per_inch
    return font_in_bp
