code: def _validate_label(self, label):
          
  
          letter_pattern = compile("^[a-z]{1}$")
          number_pattern = compile("^[0]{1}$|^[1-9]{1,2}$")
          icon_pattern = compile("^[a-zA-Z ]{1,}$")
  
          if not match(letter_pattern, label)\
              and not match(number_pattern, label)\
                  and not match(icon_pattern, label):
                      raise InvalidLabelError(
                          "{} is not a valid label".format(label)
                      )
  
          return label
docs: Validates label, raising error if invalid.