code: def _generate_namespace():
          
          raw_namespace = None
  
          # Get the Jupyter user, if available
          try:
              raw_namespace = os.environ['JPY_USER']
          except KeyError:
              pass
  
          # Otherwise get the current user
          if raw_namespace is None or raw_namespace == '':
              raw_namespace = getpass.getuser()
  
          # Remove illegal characters and return
          return re.sub(r'[^\w.-]', '-', raw_namespace)
docs: Generate an LSID namespace based off Jupyter user or system user
          :return: string