Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:Therefore, identifying protein interaction at the domain level can serve as an important intermediate step toward an effective approach for prediction of PPI [17-22], even though the inference from pairwise DDI to PPI can be complicated due to factors like the presence of multidomains, e.
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