pipeline previous next button flow to previous after reaching end and going back one #5687

# code goes here between backticks
import param
import panel as pn
pn.extension('katex')

pipeline = pn.pipeline.Pipeline()

class Stage1(param.Parameterized):

    a = param.Integer(default=2, bounds=(0, 10))
    b = param.Integer(default=3, bounds=(0, 10))

    @param.output(('c', param.Integer), ('d', param.Integer))
    def output(self):
        return self.a * self.b, self.a ** self.b

    @param.depends('a', 'b')
    def view(self):
        c, d = self.output()
        c_out = pn.pane.LaTeX('${a} * {b} = {c}$'.format(
            a=self.a, b=self.b, c=c), styles={'font-size': '2em'})
        d_out = pn.pane.LaTeX('${a}^{{{b}}} = {d}$'.format(
            a=self.a, b=self.b, d=d), styles={'font-size': '2em'})
        return pn.Column(c_out, d_out,  margin=(40, 10), styles={'background': '#f0f0f0'})

    def panel(self):
        return pn.Row(self.param, self.view,)

class Stage1B(param.Parameterized):
    a = param.Integer()
    @param.output(('c', param.Integer), ('d', param.Integer))
    def output(self):
        return self.a, 99

    @param.depends('a')
    def view(self):
        c, d = self.output()
        c_out = pn.pane.LaTeX('${a}$'.format(
            a=self.a), styles={'font-size': '2em'})
        d_out = pn.pane.LaTeX('${a} {d}$'.format(
            a=self.a, d=d), styles={'font-size': '2em'})
        return pn.Column(c_out, d_out,  margin=(40, 10), styles={'background': '#f0f0f0'})

    def panel(self):
        return pn.Row(self.param, self.view,)
class Stage2(param.Parameterized):

    c = param.Integer(default=6, bounds=(0, None))
    exp = param.Number(default=0.1, bounds=(0, 3))

    @param.depends('c', 'exp')
    def view(self):
        out = pn.pane.LaTeX('${%s}^{%s}={%.3f}$' % (self.c, self.exp, self.c**self.exp),
                      styles={'font-size': '2em'})
        return pn.Column(out, margin=(40, 10), styles={'background': '#f0f0f0'})

    def panel(self):
        return pn.Row(self.param, self.view)

pipeline.add_stage('Stage 1', Stage1)
pipeline.add_stage('Stage1B', Stage1B)
pipeline.add_stage('Stage 2', Stage2)

pipeline.show()