I would like to retrieve all the constituent bonds in a EUR Corporate bond index such as .IBBEU003D using Eikon Python API (preferred) or the Datastream Python API.

My Eikon API code attempt is as follows:

df, err = ek.get_data(
    instruments = ['.IBBEU003D'],
    fields = ['TR.PortfolioConstituentsName',
              'TR.IndexConstituentName'],
    parameters = {
        'SDate':'2006-01-02'
    }
)
df  

Certain Data items have a TR.PortfolioConstituentsName field, that comes up empty when I try to access it.