Rust Petgraph WASM Project, trying to use struct with Graph property, but requires 2 parameters

I am very new to Rust, so this might be a very rookie question.

I am trying to create a web app with rust -> wasm. Tried to follow the tutorial https://rustwasm.github.io/docs/book/introduction.html and tried to use the crate package "petgraph" I have come up with the following

use petgraph::graph::Graph;
#[wasm_bindgen]
pub struct TreeStructure {
    directed_graph: Graph
}
#[wasm_bindgen]
impl TreeStructure {
    pub fn new() -> TreeStructure {
        TreeStructure {
            directed_graph: Graph::<&str, &str>::new()
        }
    }
     pub fn addNode(&mut self, newNode: &str) {
        let findIndex = self.findNode(newNode);
        if findIndex < 0 {
            self.directed_graph.add_node(newNode);
        } else {
            alert("cant add, this {} already exist in the nodes", newNode);
        }
    }

    pub fn removeNode(&mut self, toRemoveNode: &str) {
        let findIndex = self.findNode(toRemoveNode);
        if findIndex > -1 {
            self.directed_graph.remove_node(toRemoveNode);
        } else {
            alert("cant remove, cannot find {} in the nodes", toRemoveNode);
        }
    }

    pub fn addEdge(&mut self, fromNode: &str, toNode: &str) {
        let fromIndex = self.findNode(fromNode);
        let toIndex = self.findNode(toNode);
        if fromIndex > -1 && toIndex > -1 {
            let alreadyEdged = self.directed_graph.contains_edge(fromIndex, toIndex);
            if !alreadyEdged {
                self.directed_graph.add_edge(fromIndex, toIndex, "");
            } else {
                alert("edge already exist from {} to {}", fromNode, toNode);
            }
        }
    }

    pub fn getNeighbors(&self, checkNode: &str) -> Array {
        let checkIndex = self.findNode(checkNode);
        if checkIndex < 0 {
            return vec![].into_inter().collect();
        }
        self.directed_graph.neighbors_directed(checkIndex).collect();
    }
}
impl TreeStructure {
    pub fn findNode(&self, nodeToFind: &str) -> i32 {
        let findIndex = self.directed_graph.node_indices().collect::<Vec<_>>().iter().position(|&r| r == nodeToFind);
        match findIndex {
            Some(x) => x,
            None => -1
        }
    }
}

but this is giving me compile error

error[E0107]: wrong number of type arguments: expected at least 2, found 0
--> src/lib.rs:25:25
   |
25 |         directed_graph: Graph
   |                         ^^^^^ expected at least 2 type arguments

Reading https://docs.rs/petgraph/0.5.0/petgraph/graph/struct.Graph.html I then tried

use petgraph::graph::Node;
use petgraph::graph::Edge;
pub struct TreeStructure<N: Node, E: Edge> {
    directed_graph: Graph<N, E>
}

But then it says wasm-bindgen does not support that syntax? What should I do here?

Given that your new function puts a Graph::<&str, &str> in directed_graph, that is what you should also use in the declaration:

pub struct TreeStructure {
    directed_graph: Graph<&str, &str>,
}

However, this requires you to specify a lifetime. I'm not familiar enough with wasm to say which will be best (plus it depends on what exactly you put in the graph), but you will probably need to either use a 'static lifetime:

pub struct TreeStructure {
    directed_graph: Graph<&'static str, & 'static str>,
}

which will also require you to give the 'static lifetime to your method parameters. Or you will need to move to owned strings:

pub struct TreeStructure {
    directed_graph: Graph<String, String>,
}

again with the appropriate changes to your methods.