-format: `chr2', `chr2:1000000' or `chr2:1,000,000-2,000,000'. The
-coordinate is 1-based.
+format: `chr2' (the whole chr2), `chr2:1000000' (region starting from
+1,000,000bp) or `chr2:1,000,000-2,000,000' (region between 1,000,000 and
+2,000,000bp including the end points). The coordinate is 1-based.