code: public boolean hasContact(ResidueIdentifier resId1, ResidueIdentifier resId2) {
  
  		return contacts.containsKey(new Pair<ResidueIdentifier>(resId1, resId2));
  	}
docs: Tell whether the given pair is a contact in this GroupContactSet,
  in a chain-identifier independent way: contacts happening between different copies of
  the same Compound(Entity) will be considered equal as long as they have the same
  residue numbers.
  @param resId1
  @param resId2
  @return