@Override
		public boolean isValidSourceType(SourceType sourceType, Address symbolAddress) {
			if (sourceType != SourceType.DEFAULT) {
				return true;
			}
			return symbolAddress.isExternalAddress();
		}
Class to represent the various types of Symbols.
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/symbol/SymbolType.java