code: def numeric_params(self):
          
          nparams = dict(
              D = (self.diffusion_coeff.mean(), 'Diffusion coefficient (m^2/s)'),
              np = (self.num_particles, 'Number of simulated particles'),
              t_step = (self.t_step, 'Simulation time-step (s)'),
              t_max = (self.t_max, 'Simulation total time (s)'),
              ID = (self.ID, 'Simulation ID (int)'),
              EID = (self.EID, 'IPython Engine ID (int)'),
              pico_mol = (self.concentration() * 1e12,
                          'Particles concentration (pM)'))
          return nparams
docs: A dict containing all the simulation numeric-parameters.
  
          The values are 2-element tuples: first element is the value and
          second element is a string describing the parameter (metadata).