def arcs(self):
        """Get information about the arcs available in the code.

        Returns a sorted list of line number pairs.  Line numbers have been
        normalized to the first line of multiline statements.

        """
        all_arcs = []
        for l1, l2 in self.byte_parser._all_arcs():
            fl1 = self.first_line(l1)
            fl2 = self.first_line(l2)
            if fl1 != fl2:
                all_arcs.append((fl1, fl2))
        return sorted(all_arcs)
Get information about the arcs available in the code.

        Returns a sorted list of line number pairs.  Line numbers have been
        normalized to the first line of multiline statements.