old_contents: # -*- coding: utf-8 -*-
  from __future__ import (absolute_import, division, print_function)
  import math
  
  
  def nernst_potential(ion_conc_out, ion_conc_in, charge, T,
                       constants=None, units=None, backend=math):
      """
      Calculates the Nernst potential using the Nernst equation for a particular
      ion.
  
      Parameters
      ----------
      ion_conc_out: float with unit
          Extracellular concentration of ion
      ion_conc_in: float with unit
          Intracellular concentration of ion
      charge: integer
          Charge of the ion
      T: float with unit
          Absolute temperature
      constants: object (optional, default: None)
          constant attributes accessed:
              F - Faraday constant
              R - Ideal Gas constant
      units: object (optional, default: None)
          unit attributes: coulomb, joule, kelvin, mol
      backend: module (optional, default: math)
          module used to calculate log using `log` method, can be substituted
          with sympy to get symbolic answers
  
      Returns
      -------
      Membrane potential
      """
      if constants is None:
          F = 96485.33289
          R = 8.3144598
          if units is not None:
              F *= units.coulomb / units.mol
              R *= units.joule / units.kelvin / units.mol
      else:
          F = constants.Faraday_constant
          R = constants.ideal_gas_constant
  
      return (R * T) / (charge * F) * backend.log(ion_conc_out / ion_conc_in)
  
new_contents: # -*- coding: utf-8 -*-
  from __future__ import (absolute_import, division, print_function)
  import math
  
  
  def nernst_potential(ion_conc_out, ion_conc_in, charge, T,
                       constants=None, units=None, backend=math):
      """
      Calculates the Nernst potential using the Nernst equation for a particular
      ion.
  
      Parameters
      ----------
      ion_conc_out: float with unit
          Extracellular concentration of ion
      ion_conc_in: float with unit
          Intracellular concentration of ion
      charge: integer
          Charge of the ion
      T: float with unit
          Absolute temperature
      constants: object (optional, default: None)
          constant attributes accessed:
              F - Faraday constant
              R - Ideal Gas constant
      units: object (optional, default: None)
          unit attributes: coulomb, joule, kelvin, mol
      backend: module (optional, default: math)
          module used to calculate log using `log` method, can be substituted
          with sympy to get symbolic answers
  
      Returns
      -------
      Membrane potential
      """
      if constants is None:
          F = 96485.33289
          R = 8.3144598
          if units is not None:
              F *= units.coulomb / units.mol
              R *= units.joule / units.kelvin / units.mol
      else:
          F = constants.Faraday_constant
          R = constants.molar_gas_constant
  
      return (R * T) / (charge * F) * backend.log(ion_conc_out / ion_conc_in)
  
subject: Use actual constant name (molar_gas_constant)