def string_date_range(hr_data):
    """
    Using the list of tuples from the `parse_heart_json` method, determines the date range
    of data present. Two outputs are possible:

    1) Data for only one day: Will return the one day in month-day-year format: i.e. Dec16-2019
    2) Data spanning multiple days: Will return the range in month-day-year-month-day-year format: i.e. Dec16-2019-Dec20-2019
    """

    try:
        begin_date = hr_data[0][0] # gets first element of the tuple (datetime) from first item in list
        end_date = hr_data[-1][0] # gets first element of the tuple (datetime) from last item in list
    except IndexError:
        print("An empty list of tuples was passed -- please check input data")
        return(None)
    except Exception as e:
        print("Failed to determine the date range for the data passed in: {}".format(e))
        return(None)
    
    begin_string = begin_date.strftime("%b%d-%Y")
    end_string = end_date.strftime("%b%d-%Y")

    if (begin_string == end_string):
        return(begin_string)
    else:
        return("{0}-{1}".format(begin_string, end_string))