code: public String [] getFieldsArray(){
  		Object [] obj = datapoint.keySet().toArray();
  		String [] out = new String[obj.length];
  		for(int i=0; i<obj.length; i++)
  			out[i] = String.valueOf(obj[i]);
  		return out;
  	}
docs: Returns a String array with all the Forecast.io fields available
  in this data point. It can be usefull to iterate over all
  available fields in a data point.
  
  @return the String array with the field's names.