code: def _get_default_wrapper():
      
  
      from .ctwrapper import NIVisaLibrary
      ni_binary_found = bool(NIVisaLibrary.get_library_paths())
      if ni_binary_found:
          logger.debug('The NI implementation available')
          return 'ni'
      else:
          logger.debug('Did not find NI binary')
  
      try:
          get_wrapper_class('py')  # check for pyvisa-py availability
          logger.debug('pyvisa-py is available.')
          return 'py'
      except ValueError:
          logger.debug('Did not find pyvisa-py package')
      raise ValueError('Could not locate a VISA implementation. Install either the NI binary or pyvisa-py.')
docs: Return an available default VISA wrapper as a string ('ni' or 'py').
  
      Use NI if the binary is found, else try to use pyvisa-py.
      If neither can be found, raise a ValueError.