code: def show_density_matrix(self, surface_divider = 20.0):
          
          density_matrix = self.get_density_matrix(surface_divider)
          
          plt.imshow(density_matrix, cmap = plt.get_cmap('hot'), interpolation='kaiser')
          plt.title("P-Matrix")
          plt.colorbar()
          plt.show()
docs: !
          @brief Show density matrix (P-matrix) using kernel density estimation.
          
          @param[in] surface_divider (double): Divider in each dimension that affect radius for density measurement.
          
          @see show_distance_matrix()