code: def change_length(self, parameter, value):
          r
  
          self.preamble.append(UnsafeCommand('setlength',
                                             arguments=[parameter, value]))
docs: r"""Change the length of a certain parameter to a certain value.
  
          Args
          ----
          parameter: str
              The name of the parameter to change the length for
          value: str
              The value to set the parameter to