code: def _remove_boundaries(self, interval):
          
          begin = interval.begin
          end = interval.end
          if self.boundary_table[begin] == 1:
              del self.boundary_table[begin]
          else:
              self.boundary_table[begin] -= 1
  
          if self.boundary_table[end] == 1:
              del self.boundary_table[end]
          else:
              self.boundary_table[end] -= 1
docs: Removes the boundaries of the interval from the boundary table.