Improved plot that allows to plot polygons and holes in
        different colors.
        
        :param c_poly: Polygons color.
        :type c_poly: matplotlib color, 'default' or 't' (transparent)
        :param c_holes: Holes color.
        :type c_holes: matplotlib color, 'default' or 't' (transparent)
        :param ret: If True, returns the figure. It can be used to add 
            more elements to the plot or to modify it.
        :type ret: bool
        :param ax: If a matplotlib axes given, this method will 
            represent the plot on top of this axes. This is used to
            represent multiple plots from multiple geometries, 
            overlapping them recursively.
        :type ax: mplot3d.Axes3D, None
        :returns: None, axes
        :rtype: None, mplot3d.Axes3D

def iplot(self, c_poly='default', c_holes='c', ret=False, ax=None):
        """
        Improved plot that allows to plot polygons and holes in
        different colors.
        
        :param c_poly: Polygons color.
        :type c_poly: matplotlib color, 'default' or 't' (transparent)
        :param c_holes: Holes color.
        :type c_holes: matplotlib color, 'default' or 't' (transparent)
        :param ret: If True, returns the figure. It can be used to add 
            more elements to the plot or to modify it.
        :type ret: bool
        :param ax: If a matplotlib axes given, this method will 
            represent the plot on top of this axes. This is used to
            represent multiple plots from multiple geometries, 
            overlapping them recursively.
        :type ax: mplot3d.Axes3D, None
        :returns: None, axes
        :rtype: None, mplot3d.Axes3D
        """
        # Default parameter
        if c_holes == 'default': c_holes = 'c' # cyan for the holes
        
        seed = self.get_seed()
        if c_poly != False:
            ax = Surface(seed['polygons']).plot(color=c_poly, ret=True,
                                                ax=ax)
        if self.holes != [] and c_holes != False:
            ax = Surface(seed['holes']).plot(color=c_holes, ret=True,
                                             ax=ax)
        if ret: return ax