code: def get_internals(model):
      
      biomass = set(find_biomass_reaction(model))
      if len(biomass) == 0:
          LOGGER.warning("No biomass reaction detected. Consistency test results "
                         "are unreliable if one exists.")
      return set(model.reactions) - (set(model.boundary) | biomass)
docs: Return non-boundary reactions and their metabolites.
  
      Boundary reactions are unbalanced by their nature. They are excluded here
      and only the metabolites of the others are considered.
  
      Parameters
      ----------
      model : cobra.Model
          The metabolic model under investigation.