code: public static ChemComp getEmptyChemComp(){
  		ChemComp comp = new ChemComp();
  
  		comp.setOne_letter_code("?");
  		comp.setThree_letter_code("???"); // Main signal for isEmpty()
  		comp.setPolymerType(PolymerType.unknown);
  		comp.setResidueType(ResidueType.atomn);
  		return comp;
  	}
docs: Creates a new instance of the dummy empty ChemComp.
  @return