Suppose we have a list of schools like this one:

```
[
{
    "school_name” : "School #1",
    "city” : "Frankfurt",
    "country” : "Germany",
},
{
    "school_name” : "School #2",
    "city” : "Frankfurt",
    "country” : "Germany",
},
{
    "school_name” : "School #3",
    "city” : "Madrid",
    "country” : "Spain",
},
{
    "School_name” : "School #4",
    "city” : "Barcelona",
    "country” : "Spain",
}

```

]

Would it be possible with aggregation framework to get a unique list of cities by country like this one:

```
[
{
 "country" : "Germany" 
 "cities" : [Frankfurt,Berlin, ...]
},
{
 "country" : "Spain",
 "cities" : [Madrid,Barcelona, ...]
}

```

]