How can I get json param

`test.py`
```
import fire

def hello(name):
print(name)
print(name.get('a'))

if __name__ == "__main__":
fire.Fire(hello)
```
example:
```
python test.py '{"a":"aaa","b":[1,2,3]}'
```
the param `name` is json dict, result print:
```
{'a':'aaa','b':[1,2,3]}
'aaa'
```
but when input:
```
python test.py '{"a":"aa.a","b":[1,2,3]}'
```
the param `name` can't parse to json, it's a `str`,how can I get the json param??
```
{a:aa.a,b:[1,2,3]}
```