title: Download GenBank sequence file within python script using only the accession number
body: <p>Assume the input to a python script is a GenBank accession number such as n</p>
  <p>.
  How do I use only that accession number to download the file? I know I can use Bio::DB::EUtilities, but it seems to require  a ID.  Can the accession number be used instead of a numeric ID?
  The code to download a file is</p>
  <pre><code>my @ids = qw(1621261 89318838 68536103 20807972 730439);
  
  my $factory = Bio::DB::EUtilities-&gt;new(-eutil   =&gt; 'efetch',
                                         -db      =&gt; 'protein',
                                         -rettype =&gt; 'gb',
                                         -email   =&gt; 'mymail@foo.bar',
                                         -id      =&gt; \@ids);
  </code></pre>
  <p>The ids are all 7 digit numbers in the above example.
  Can I set -id =&gt; AF405666.1 to fetch a single Genbank file?</p>