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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def forward(self, step):
 """Move the turtle forward. :param step: Integer. Distance to move forward. """

        x = self.pos_x + math.cos(math.radians(self.rotation)) * step
        y = self.pos_y + math.sin(math.radians(self.rotation)) * step
        prev_brush_state = self.brush_on
        self.brush_on = True
        self.move(x, y)
        self.brush_on = prev_brush_state