public FunctionRecord getFunctionByID(long functionID) throws IOException {
		FunctionRecord functionRecord = functionCache.get(functionID);
		if (functionRecord == null) {
			DBRecord record = table.getRecord(functionID);
			if (record != null) {
				functionRecord = new FunctionRecord(fidDb, functionCache, record);
			}
		}
		return functionRecord;
	}
Returns a single function record given its id, or null if no such record exists.
@param functionID the function record primary key id
@return the function record or null if non-existent
@throws IOException if database seek encounters an error
Ghidra/Features/FunctionID/src/main/java/ghidra/feature/fid/db/FunctionsTable.java