ing sequence. Mappings can be defined in one of the
following two forms:</p></div>
<div class="literalblock">
<div class="content">
<pre><tt>mapping = {
  chr1  = "hs_ref_chr1.fa.gz",
  chr2  = "hs_ref_chr2.fa.gz"
}</tt></pre>
</div></div>
<div class="paragraph"><p>or</p></div>
<div class="literalblock">
<div class="content">
<pre><tt>function mapping(sequence_region)
  return "hs_ref_"..sequence_region..".fa.gz"
end</tt></pre>
</div></div>
<div class="paragraph"><p>The first form defines a 