'Adds timestamped data to a field
Arguments:
name      -- Name of the field
timestamp -- Timestamp for the data (string)
value     -- Field value at the timestamp
flags     -- [optional] data classifier flags for the field, e.g. momentary
Formatted as a dictionary like { "flag name": "flag value" ... }'

def _add_field_timestamp_data(self, name, timestamp, value, flags=None):

    if (not (name in self.fields.keys())):
        return False
    if (not (timestamp in self.timestamp_data)):
        self.timestamp_data[timestamp] = {}
    self.timestamp_data[timestamp][name] = {'value': value, 'flags': flags}
    return True
