cannot import function from module

I import this module in the main program with the line from classe_recto2 import Recto. It will import the class Recto (I can print a class Recto object) but when I call the function next_circle I get NameError: name 'next_circle' is not defined. The whole module looks like this:

import pygame

class Recto:
    
    def __init__(self,posizione, colore,snippet,circles_list, counter_snippet, volume):
        self.posizione = posizione
        self.colore = colore
        self.snippet = snippet
        self.cerchi = circles_list
        self.counter_snippet = counter_snippet
        self.volume = volume
        self.first_position = self.cerchi[0][0]
        self.position = self.cerchi[0][1]
        self.height = self.cerchi[0][2]
        self.direzione = self.cerchi[0][3]
   
    def snippet_volume(self):
        pygame.mixer.Sound.set_volume(self.snippet, self.volume)
        
    def next_circle(self):
        circle = []
        if self.height == 0:
            new_height = 0
            self.height = new_height
        else:    
            new_height = self.height -2
            self.height = new_height
        if self.direzione == 1 and self.position < self.first_position +100:
            new_position = self.position+10
            self.position = new_position
            if new_position > self.first_position +100:
                new_position = self.first_position +100
                self.position = new_position
                self.direzione = -1
            else:    
                self.direzione = 1
        if self.position == self.first_position +100:
            new_position = self.position -10
            self.position = new_position
            self.direzione = -1
        if self.direzione == -1 and self.position > self.first_position:
            new_position = position -10
            if new_position < self.first_position:
                new_position = self.first_position
                self.position = new_position
                self.direzione= 1
            else:    
                self.direzione = -1
        if self.direzione == -1 and self.position == self.first_position:    
            new_position = self.position+10
            self.position = new_position
            self.direzione = 1
        circle.append(self.first_position)
        circle.append(new_position)
        circle.append(new_height)
        circle.append(self.direzione)
        return circle  

Sorry, I know it is a lot of code but I thought being able to see it all could make it easier to pinpoint the problem. Thank you.