insert method
Implementation
void insert(String key, dynamic value) {
_cache.remove(key);
Node node = _root;
if (node.keys.contains(key)) {
node.values[node.keys.indexOf(key)] = value;
} else {
if (node.keys.length == 2 * _degree - 1) {
Node newNode = Node(tLeaf: false);
newNode.children.add(node);
_splitChild(node, 0);
_insertNonFull(newNode, key, value);
_root = newNode;
} else {
_insertNonFull(node, key, value);
}
}
}