Update comment for seq-iterator.
Update comment for seq-iterator.

acthp/ucsc-xena-server,ucscXena/ucsc-xena-server,acthp/ucsc-xena-server,ucscXena/ucsc-xena-server,ucscXena/ucsc-xena-server,ucscXena/ucsc-xena-server,acthp/ucsc-xena-server,ucscXena/ucsc-xena-server,acthp/ucsc-xena-server,acthp/ucsc-xena-server