I have a hashmap

```
{
k1 = {v1, v2},
k2 = {v2},
k3 = {v1}
}

```

and my requirement is build a new hashmap with values in old map as keys and keys as list of values. 
New hasmap would look like

```
{
v1 = {k1, k3},
v2 = {k1, k2}
}

```