f the range
    # so we check in addition that the end is larger than the start of the range.
    # NOTE: if the given range has zero length, then any annotation that starts before or at start
    # AND ends at or after start==end is overlapping
    if start == end:
        # in order to check what is overlapping with the zero length span, we need to find
        # intervals which start before the start of that span AND end at least one after that span;
        # or intervals which start at the span and end