def preparer_graphe(G):
    """Nettoie et prépare le graphe pour l'analyse."""
    niveaux_temp = {
        node: int(str(attrs.get("niveau")).strip('"'))
        for node, attrs in G.nodes(data=True)
        if attrs.get("niveau") and str(attrs.get("niveau")).strip('"').isdigit()
    }
    G.remove_nodes_from([n for n in G.nodes() if n not in niveaux_temp])
    G.remove_nodes_from(
        [n for n in G.nodes() if niveaux_temp.get(n) == 10 and 'Reserves' in n])
    return G, niveaux_temp