public addAirline(airline: AddAirline): Observable<any> {
        return this.apollo.mutate({
            mutation: gql`
                mutation($name: String!, $color: String!) {
                    createAirline(name: $name, color: $color){
                        id,
                        name,
                        color
                    }
                }
            `,
            variables: {
                name: airline.name,
                color: airline.color
            },
            update: (proxy, { data: { createAirline } }) => {
                // Read the data from our cache for this query.
                const data: IAirlines = proxy.readQuery({query: this.getAirlines});
                data.allAirlines.push(createAirline);

                // Write our data back to the cache.
                proxy.writeQuery({ query: this.getAirlines, data });
            }
        });
    }