Check if an xref exists when inserting, if not use the new ID, if it does exist, use the existing xref_id.
Check if an xref exists when inserting, if not use the new ID, if it does exist, use the existing xref_id.

Ensembl/ensembl,james-monkeyshines/ensembl,willmclaren/ensembl,james-monkeyshines/ensembl,willmclaren/ensembl,muffato/ensembl,mjg17/ensembl,Ensembl/ensembl,james-monkeyshines/ensembl,danstaines/ensembl,at7/ensembl,danstaines/ensembl,at7/ensembl,muffato/ensembl,mjg17/ensembl,Ensembl/ensembl,mjg17/ensembl,muffato/ensembl,at7/ensembl,mjg17/ensembl,muffato/ensembl,danstaines/ensembl,Ensembl/ensembl,james-monkeyshines/ensembl,at7/ensembl