code: @SuppressWarnings("unchecked")
  	public Map<String, ?> decodeSignedRequest(String signedRequest) throws SignedRequestException {
  		return decodeSignedRequest(signedRequest, Map.class);
  	}
docs: Decodes a signed request, returning the payload of the signed request as a Map
  @param signedRequest the value of the signed_request parameter sent by Facebook.
  @return the payload of the signed request as a Map
  @throws SignedRequestException if there is an error decoding the signed request