@Override
	public Function getFunction(long key) {
		lock.acquire();
		try {
			lastFuncID = key;
			FunctionDB func = cache.get(key);
			if (func == null) {
				try {
					DBRecord rec = adapter.getFunctionRecord(key);
					if (rec != null) {
						func = new FunctionDB(this, cache, addrMap, rec);
					}
				}
				catch (IOException e) {
					dbError(e);
				}
			}
			return func;
		}
		finally {
			lock.release();
		}
	}
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