What is the defining Set in NLP I am reading the paper Man is to Computer Programmer as Woman is to Homemaker? Debiasing Word Embeddings here is the pdf.

On page 6, we read: 

Step 1: Identify gender subspace. Inputs: word sets W , defining sets D_1 , ..., D_m. 


However, they paper before and after this statement does not mention what these defining sets are? Can anyone give me a definition or description of these sets?

Thank you.
If you read the following sentence at the first line of section 6:


  The debiasing algorithms are defined in terms of sets of words rather than just pairs, for generality, so that we can consider other biases such as racial or religious biases.


$D_1, D_2, \ldots, D_m$ are the set of words, in general, to be considered in the de-biasing algorithm, instead of considering a pair of words such as Computer Programmer and Houseworker for the de-biasing genders of man and woman. Hence, one of $D$s could be {'Computer Programmer', 'Houseworker'}, here, as an example.