Add indexed position query.
Add indexed position query.

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