[web2py] IS_IN_DB Referencing Label

[Kostas M]

I have a table Lab_members:
db.define_table('lab_members', 
                Field('member',db.auth_user,
                      represent=lambda member,row: str(member.username)
                        ),    
                )

and now I create a second table, having a Field:
                Field('member',db.lab_members,label='Lab member',
                      represent=lambda member,row: 
db.auth_user(member).username,
                      
requires=IS_IN_DB(db((db.lab_members.lab==auth.user_id)),
                                        field='lab_members.member', 
                                        label='%(member)s',
                                        )

My problem is, how to set the label in the IS_IN_DB validator, as to 
display in the dropdown list the usernames and not the user.id ?
After the selection, the usernames are displayed properly (through the 
represent function of the field).

Is there any solution?

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