`Organization` and `Link` are associated through `Node`. 

`Organization`:

```
has_many :nodes
has_many :links, through: :nodes, source: :where_first_links

```

`Node`:

```
belongs_to :organization
has_many :where_first_links, class_name:  "Link",
                             foreign_key: "first_node_id"
has_many :where_second_links, class_name:  "Link",
                              foreign_key: "second_node_id"

```

`Link`:

```
belongs_to :first_node,  class_name: "Node"
belongs_to :second_node, class_name: "Node"

```

**Question:**: How can I associate `Link` back to `Organization`? I tried the line below but that does not seem to work (`ArgumentError: Unknown key: :through.`):

```
belongs_to :organization, 
           through: :first_node, 
           source: :where_first_links, 
           inverse_of: :links

```