gistfile1.txt

I'm using RestKit 0.10.2. 
I have the following JSON data:

    {
      "title":"2012 General Election: Romney vs. Obama",
      "last_updated":"2012-01-02T17:08:44Z",
      "estimates":[
        { "choice":"Romney", "value":44.5 },
        { "choice":"Obama", "value":46.6 }
      ],
      "estimates_by_date":[
        { "date":"2012-06-28", 
          "estimates":[
            { "choice":"Romney", "value":44.5 },
            { "choice":"Obama", "value":46.6 }
          ]
        },
        { "date":"2012-06-27",
          "estimates":[
            { "choice":"Romney", "value":44.5 },
            { "choice":"Obama", "value":46.5 }
          ]
        }
      ]
    }

I currently have a `Chart` class and an `Estimate` class. I've correctly set up the mappings to load the `estimates` attribute on `Chart` with an array of `Estimate` objects.

    RKObjectMapping *estimateMapping = [RKObjectMapping mappingForClass:[Estimate class]];
    [estimateMapping mapAttributes:@"value", @"choice", nil];
        
    RKObjectMapping *chartMapping = [RKObjectMapping mappingForClass:[Chart class]];
    [chartMapping mapAttributes:@"title", @"last_updated", nil];
    [chartMapping mapKeyPath:@"estimates" toRelationship:@"estimates" withMapping:estimateMapping];

However, there are also `estimates_by_date`. 

How can I load the array of `estimates_by_date` into an `NSDictionary` on `Chart` where the `date` is the key and an `Estimate` object is the value?