groupBy(array: any[], property: string) {
    return array.reduce((prev, next) => {
        // If the group doesn't exist, create it
        if(!prev[property]) { prev[property] = [next]; }
        // Else, we push it in
        else { prev[property].push(next); }
        // Mandatory return
        return prev;
    }, {});
}
public getpeople(people:Person[]):Person[]
{
  return groupby(people.filter((person: Person) => person.age>30 && person.age<40), "gender");
}