private SubMemoryBlock createBufferSubBlock(long parentKey, long offset, long length,
			InputStream is) throws IOException {
		DBBuffer buffer = createBuffer(length, is);
		DBRecord record =
			createSubBlockRecord(parentKey, offset, length, V3_SUB_TYPE_BUFFER, buffer.getId(), 0);
		return new BufferSubMemoryBlock(this, record);
	}
MemoryMap adapter for version 3.
This version introduces the concept of sub memory blocks and FileBytes
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/mem/MemoryMapDBAdapterV3.java