How to build a graph database with Flutter

In this article I will go over how to create and use a graph database with Flutter.

TLDR The final source here and an online demo.

Prerequisites 

Flutter installed and setup (Refer to this article if you need help).

Basic knowledge of SQLite.

Basic knowledge of Graph Databases (Refer to this video if you need to learn more).

Overview 

First of all, why do we need a graph database when other storage options exist?