docs: def toString(self):
          """
          Return the key sequence as a human readable string, eg. "<ctrl>+x".
  
          Note that this list is suitable as an argument to
          QtmacsKeysequence, which would create another object
          representing the same key sequence. If a key could not be
          converted then it will be displayed as '<Unknown>'. If this
          happens, then the key map in ``qte_global.default_qt_keymap``
          is incomplete and should be amended accordingly.
  
          |Args|
  
          * **None**
  
          |Returns|
  
          **str**: the key sequence, eg. '<ctrl>+f', or '<F1>', or
            '<Unknown>'.
  
          |Raises|
  
          * **None**
          """
          # Initialise the final output string.
          retVal = ''
  
          for mod, key in self.keylistQtConstants:
              out = ''
              # Check for any modifiers except <shift> and add the
              # corresponding string.
              if (mod & QtCore.Qt.ControlModifier):
                  out += '<Ctrl>+'
              if (mod & QtCore.Qt.AltModifier):
                  out += '<Alt>+'
              if (mod & QtCore.Qt.MetaModifier):
                  out += '<Meta>+'
              if (mod & QtCore.Qt.KeypadModifier):
                  out += '<Keypad>+'
              if (mod & QtCore.Qt.GroupSwitchModifier):
                  out += '<GroupSwitch>+'
  
              # Format the string representation depending on whether or
              # not <Shift> is active.
              if (mod & QtCore.Qt.ShiftModifier):
                  # If the key with the shift modifier exists in the
                  # reverse dictionary then use that string, otherwise
                  # construct it manually be printing the modifier and
                  # the key name. The first case is typically
                  # encountered for upper case characters, where eg. 'F'
                  # is preferable over '<Shift>+f'.
                  if (QtCore.Qt.ShiftModifier, key) in self.keyDictReverse:
                      # The shift-combined key exists in the dictionary,
                      # so use it.
                      out += self.keyDictReverse[(QtCore.Qt.ShiftModifier, key)]
                  elif (QtCore.Qt.NoModifier, key) in self.keyDictReverse:
                      # The shift-combined key does not exists in the
                      # dictionary, so assemble the modifier and key by
                      # hand.
                      out += ('<Shift>+' +
                              self.keyDictReverse[(QtCore.Qt.NoModifier, key)])
                  else:
                      out += '<Unknown>'
              else:
                  if (QtCore.Qt.NoModifier, key) in self.keyDictReverse:
                      out += self.keyDictReverse[(QtCore.Qt.NoModifier, key)]
                  else:
                      out += '<Unknown>'
  
              # Add a spacer.
              retVal += out + ' '
  
          # Return the final string (minus the last spacer).
          return retVal[:-1]