code: def plot(self, xmin, xmax, idx_input=0, idx_output=0, points=100,
               **kwargs) -> None:
          
          xs_ = numpy.linspace(xmin, xmax, points)
          ys_ = numpy.zeros(xs_.shape)
          for idx, x__ in enumerate(xs_):
              self.inputs[idx_input] = x__
              self.process_actual_input()
              ys_[idx] = self.outputs[idx_output]
          pyplot.plot(xs_, ys_, **kwargs)
docs: Plot the relationship between a certain input (`idx_input`) and a
          certain output (`idx_output`) variable described by the actual
          |anntools.ANN| object.
  
          Define the lower and the upper bound of the x axis via arguments
          `xmin` and `xmax`.  The number of plotting points can be modified
          by argument `points`.  Additional `matplotlib` plotting arguments
          can be passed as keyword arguments.