Make _tables(), _columns(), and _left_join() readable.
Make _tables(), _columns(), and _left_join() readable.

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