'The plot interval for the default geometric plot of the polygon.
Parameters
parameter : str, optional
Default value is \'t\'.
Returns
plot_interval : list (plot interval)
[parameter, lower_bound, upper_bound]
Examples
>>> from sympy import Polygon
>>> p = Polygon((0, 0), (1, 0), (1, 1))
>>> p.plot_interval()
[t, 0, 1]'

def plot_interval(self, parameter='t'):

    t = Symbol(parameter, real=True)
    return [t, 0, 1]
