code: def __get_average_inter_cluster_distance(self, entry):
          
          
          linear_part_distance = sum(list_math_multiplication(self.linear_sum, entry.linear_sum));
          
          return ( (entry.number_points * self.square_sum - 2.0 * linear_part_distance + self.number_points * entry.square_sum) / (self.number_points * entry.number_points) ) ** 0.5;
docs: !
          @brief Calculates average inter cluster distance between current and specified clusters.
          
          @param[in] entry (cfentry): Clustering feature to which distance should be obtained.
          
          @return (double) Average inter cluster distance.