old_contents: from .simulation import Simulation3DCellCentered, Simulation3DNodal
  from .simulation_2d import Simulation2DCellCentered, Simulation2DNodal
  from .survey import Survey, from_dc_to_ip_survey
  from .run import run_inversion
  
  Simulation2DCellCentred = Simulation2DCellCentered
  Simulation3DCellCentred = Simulation2DCellCentered
  
  ############
  # Deprecated
  ############
  from .simulation import Problem3D_CC, Problem3D_N
  from .simulation_2d import Problem2D_CC, Problem2D_N
  
new_contents: from .simulation import Simulation3DCellCentered, Simulation3DNodal
  from .simulation_2d import Simulation2DCellCentered, Simulation2DNodal
  from .survey import Survey, from_dc_to_ip_survey
  from .run import run_inversion
  from ..resistivity import receivers
  from ..resistivity import sources
  
  Simulation2DCellCentred = Simulation2DCellCentered
  Simulation3DCellCentred = Simulation2DCellCentered
  
  ############
  # Deprecated
  ############
  from .simulation import Problem3D_CC, Problem3D_N
  from .simulation_2d import Problem2D_CC, Problem2D_N
  
subject: add sources and receivers from static under the ip namespace