docs: private boolean checkCode(List<ValidationMessage> errors, Element element, String path, String code, String system, String display) {
  		long t = System.nanoTime();
  		boolean ss = context.supportsSystem(system);
  		txTime = txTime + (System.nanoTime() - t);
  		if (ss) {
  			t = System.nanoTime();
  			ValidationResult s = context.validateCode(system, code, display);
  			txTime = txTime + (System.nanoTime() - t);
  			if (s == null || s.isOk())
  				return true;
  			if (s.getSeverity() == IssueSeverity.INFORMATION)
  				hint(errors, IssueType.CODEINVALID, element.line(), element.col(), path, s == null, s.getMessage());
  			else if (s.getSeverity() == IssueSeverity.WARNING)
  				warning(errors, IssueType.CODEINVALID, element.line(), element.col(), path, s == null, s.getMessage());
  			else
  				return rule(errors, IssueType.CODEINVALID, element.line(), element.col(), path, s == null, s.getMessage());
  			return true;
  		} else if (system.startsWith("http://hl7.org/fhir")) {
  			if (system.equals("http://hl7.org/fhir/sid/icd-10"))
  				return true; // else don't check ICD-10 (for now)
  			else {
  				CodeSystem cs = getCodeSystem(system);
  				if (warning(errors, IssueType.CODEINVALID, element.line(), element.col(), path, cs != null, "Unknown Code System " + system)) {
  					ConceptDefinitionComponent def = getCodeDefinition(cs, code);
  					if (warning(errors, IssueType.CODEINVALID, element.line(), element.col(), path, def != null, "Unknown Code (" + system + "#" + code + ")"))
  						return warning(errors, IssueType.CODEINVALID, element.line(), element.col(), path, display == null || display.equals(def.getDisplay()), "Display should be '" + def.getDisplay() + "'");
  				}
  				return false;
  			}
  		} else if (system.startsWith("http://loinc.org")) {
  			return true;
  		} else if (system.startsWith("http://unitsofmeasure.org")) {
  			return true;
  		} else
  			return true;
  	}