def _add_boundaries(self, interval):
        """
        Records the boundaries of the interval in the boundary table.
        """
        begin = interval.begin
        end = interval.end
        if begin in self.boundary_table:
            self.boundary_table[begin] += 1
        else:
            self.boundary_table[begin] = 1

        if end in self.boundary_table:
            self.boundary_table[end] += 1
        else:
            self.boundary_table[end] = 1
Records the boundaries of the interval in the boundary table.