code: def user_hostname(self, vm_name=None):
          '''
          Return a string combining user and hostname, e.g. 'vagrant@127.0.0.1'.
          This string is suitable for use in an ssh commmand.  If user is None
          or empty, it will be left out of the string, e.g. 'localhost'.  If
          hostname is None, have bigger problems.
  
          Raises an Exception if the Vagrant box has not yet been created or
          has been destroyed.
          '''
          user = self.user(vm_name=vm_name)
          user_prefix = user + '@' if user else ''
          return user_prefix + self.hostname(vm_name=vm_namef user_hostname(self, vm_name=None):
          '''
          Return a string combining user and hostname, e.g. 'vagrant@127.0.0.1'.
          This string is suitable for use in an ssh commmand.  If user is None
          or empty, it will be left out of the string, e.g. 'localhost'.  If
          hostname is None, have bigger problems.
  
          Raises an Exception if the Vagrant box has not yet been created or
          has been destroyed.
          '''
          user = self.user(vm_name=vm_name)
          user_prefix = user + '@' if user else ''
          return user_prefix + self.hostname(vm_name=vm_name)
docs: Return a string combining user and hostname, e.g. 'vagrant@127.0.0.1'.
          This string is suitable for use in an ssh commmand.  If user is None
          or empty, it will be left out of the string, e.g. 'localhost'.  If
          hostname is None, have bigger problems.
  
          Raises an Exception if the Vagrant box has not yet been created or
          has been destroyed.