code: def delete_one_letter(self, letter=RIGHT):
          
  
          assert letter in (self.RIGHT, self.LEFT)
  
          if letter == self.LEFT:
              papy = self.cursor
              self.text = self.text[:self.cursor - 1] + self.text[self.cursor:]
              self.cursor = papy - 1
  
          else:
              self.text = self.text[:self.cursor] + self.text[self.cursor + 1:]
docs: Delete one letter the right or the the left of the cursor.