<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def remove_polyx_regions(in_file, items):
 """Remove polyX stretches, contributing to long variant runtimes. """

    ex_bed = tz.get_in(["genome_resources", "variation", "polyx"], items[0])
    if ex_bed and os.path.exists(ex_bed):
        return _remove_regions(in_file, [ex_bed], "nopolyx", items[0])
    else:
        return in_file