@Override
	public FixedKeyRecordNode getLeafNode(Field key) throws IOException {
		FixedKeyNode node = nodeMgr.getFixedKeyNode(getBufferId(getIdIndex(key)));
		node.parent = this;
		return (FixedKeyRecordNode) node.getLeafNode(key);
	}
Split this interior node and insert new child entry (key and buffer ID).  
Assumes 3 or more child keys exist in this node.
@param newKey new child key 
@param newId new child node's buffer ID
@return root node.
@throws IOException thrown if IO error occurs
Ghidra/Framework/DB/src/main/java/db/FixedKeyInteriorNode.java