@Override
	public Function getReferencedFunction(Address address) {
		Function function = getFunctionAt(address);
		if (function != null) {
			return function;
		}
		Data data = codeMgr.getDataContaining(address);
		if (data == null) {
			return null;
		}
		Reference ref = program.getReferenceManager().getPrimaryReferenceFrom(address, 0); // assume data reference hanging on data operand
		return ref != null ? getFunctionAt(ref.getToAddress()) : null;
	}
Get the function with the given key.
@param key ID of the function; ID is obtained by calling
Function.getID()
@return null if there is no function with the given key
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/function/FunctionManagerDB.java