code: public JvmOperation findImplementingOperation(LightweightTypeReference functionType) {
  		// avoid to trigger resolution of currently unbound type arguments
  		// since the computation of this' lambdas type may enhance the information
  		// about the given unbound type
  		if (functionType.getKind() == LightweightTypeReference.KIND_UNBOUND_TYPE_REFERENCE && !functionType.isResolved()) {
  			JvmOperation result = findImplementingOperation((UnboundTypeReference)functionType);
  			if (result != null) {
  				return result;
  			}
  		} 
  		List<JvmType> rawTypes = functionType.getRawTypes();
  		JvmOperation result = findImplementingOperation(rawTypes);
  		return result;
  	}
docs: /* @Nullable