Mapping of Mappings

Mark McGwire: {hr: 65, avg: 0.278}
Sammy Sosa: {
    hr: 63,
    avg: 0.288
  }

#↓ Equivalent JSON

{
  "Mark McGwire": {
    "hr": 65,
    "avg": 0.278
  },
  "Sammy Sosa": {
    "hr": 63,
    "avg": 0.288
  }
}