old_contents: from biothings.hub.datatransform.datatransform import DataTransform
  from biothings.hub.datatransform.datatransform import IDStruct
  from biothings.hub.datatransform.datatransform import DataTransformEdge
  from biothings.hub.datatransform.datatransform import RegExEdge
  from biothings.hub.datatransform.datatransform import nested_lookup
  
  # only for testing purpose, this one is not optimized
  #from biothings.hub.datatransform.datatransform_serial import DataTransformSerial
  
  from biothings.hub.datatransform.datatransform_mdb import DataTransformMDB
  from biothings.hub.datatransform.datatransform_mdb import MongoDBEdge
  from biothings.hub.datatransform.datatransform_mdb import CIMongoDBEdge
  
  # case-insensitive IDStruct class
  from biothings.hub.datatransform.ciidstruct import CIIDStruct
  
  # this involved biothings client dependency, skip it for now
  #from biothings.hub.datatransform.datatransform_api import MyChemInfoEdge
  #from biothings.hub.datatransform.datatransform_api import MyGeneInfoEdge
  
new_contents: from biothings.hub.datatransform.datatransform import DataTransform
  from biothings.hub.datatransform.datatransform import IDStruct
  from biothings.hub.datatransform.datatransform import DataTransformEdge
  from biothings.hub.datatransform.datatransform import RegExEdge
  from biothings.hub.datatransform.datatransform import nested_lookup
  
  # only for testing purpose, this one is not optimized
  #from biothings.hub.datatransform.datatransform_serial import DataTransformSerial
  
  from biothings.hub.datatransform.datatransform_mdb import DataTransformMDB
  from biothings.hub.datatransform.datatransform_mdb import MongoDBEdge
  from biothings.hub.datatransform.datatransform_mdb import CIMongoDBEdge
  
  # case-insensitive IDStruct class
  from biothings.hub.datatransform.ciidstruct import CIIDStruct
  
  # this involved biothings client dependency, skip it for now
  from biothings.hub.datatransform.datatransform_api import MyChemInfoEdge
  from biothings.hub.datatransform.datatransform_api import MyGeneInfoEdge
  
subject: fix an error during doc building