def extract_flags_from_text(self, text):
        """
        Extract the flags from the given text and return a :class:`set` of flag values. See
        :class:`~taxi.timesheet.lines.Entry` for a list of existing flags.
        """
        flags = set()
        reversed_flags_repr = {v: k for k, v in self.flags_repr.items()}
        for flag_repr in text:
            if flag_repr not in reversed_flags_repr:
                raise KeyError("Flag '%s' is not recognized" % flag_repr)
            else:
                flags.add(reversed_flags_repr[flag_repr])

        return flags