Return the key attribute to determine how data is sorted.
        Time will need to be converted to 24 hour time.
        In instances when float attributes will have an 'n/a' string, return 0.

def sort_func(self, entry):
        """Return the key attribute to determine how data is sorted.
        Time will need to be converted to 24 hour time.
        In instances when float attributes will have an 'n/a' string, return 0.
        """
        key = entry[self.sort]

        if self.sort in FLOAT_ATTRIBUTES and not isinstance(key, float):
            return 0  # If value is 'n/a' string
        elif self.sort == 'time':
            return convert_time(key)
        elif self.sort == 'date':
            return convert_date(key)

        return key