code: def get_preferred_submodules():
      
      # Path to the modules database
      modules_path = get_conf_path('db')
  
      # Modules database
      modules_db = PickleShareDB(modules_path)
  
      if 'submodules' in modules_db:
          return modules_db['submodules']
  
      submodules = []
  
      for m in PREFERRED_MODULES:
          submods = get_submodules(m)
          submodules += submods
      
      modules_db['submodules'] = submodules
      return submodules
docs: Get all submodules of the main scientific modules and others of our
      interest