Python sql行中的web2py异常

当我执行以下代码时：

family_members =db(db.member.id == membership_id).select
(db.member.name,db.member.id)
family_members.colnames = ('Name','Membership ID')

它会导致以下错误

Traceback (most recent call last):
  File "/home/abeer/Desktop/web2py/New_version/web2py_src/web2py/gluon/
restricted.py", line 184, in restricted
  File "/home/abeer/Desktop/resources/web2py/New_version/web2py_src/
web2py/applications/init/views/default/updateMember.html", line 142,
in <module>
  File "/home/abeer/Desktop/web2py/New_version/web2py_src/web2py/gluon/
globals.py", line 112, in write
  File "/home/abeer/Desktop/web2py/New_version/web2py_src/web2py/gluon/
html.py", line 103, in xmlescape
  File "/home/abeer/Desktop/web2py/New_version/web2py_src/web2py/gluon/
sql.py", line 3326, in xml
  File "/home/abeer/Desktop/web2py/New_version/web2py_src/web2py/gluon/
sqlhtml.py", line 980, in __init__
  File "/home/abeer/Desktop/web2py/New_version/web2py_src/web2py/gluon/
sql.py", line 621, in __getattr__
  KeyError: '_extra'

注意：当我对行family_members.colnames='Name'，'membershid'，进行注释时，它工作正常，但我不明白为什么。

不要使用colnames。该属性是web2py的内部属性。根据需要使用db.table.field.label='..'或SQLTABLErows，headers={…}