Bug summary

Traceback (most recent call last):
File "slider.py", line 318, in
plot_functions_3D(functions_list, colors_list)
File "slider.py", line 181, in plot_functions_3D
add_arrow_3d(line3d, d=10)
File "slider.py", line 88, in add_arrow_3d
zdata = line.get_zdata()
AttributeError: 'Line3D' object has no attribute 'get_zdata'

Code for reproduction

ax_main = fig.add_subplot(111, projection='3d')  # Use 3D projection
   for function in list_functions:
        result = [function(ti) for ti in t]
        x, y, z = zip(*result)
        line, = ax_main.plot(x, y, z)  # Use plot() for 3D plot
        add_arrow_3d(line, d=10)
        lines.append(line)

def add_arrow_3d(line):
    """
    Add an arrow to a line in a 3D plot every d steps.
    xdata = line.get_xdata()
    ydata = line.get_ydata()
    zdata = line.get_zdata() # -> error


seems not coherent here in art3D.py 
 @artist.allow_rasterization
    def draw(self, renderer):
        xs3d, ys3d, zs3d = self._verts3d
        xs, ys, zs = proj3d.proj_transform(xs3d, ys3d, zs3d, self.axes.M)
        self.set_data(xs, ys) #-> zs is not used
        super().draw(renderer)
        self.stale = False

and here : 
    def set_3d_properties(self, zs=0, zdir='z'):
        xs = self.get_xdata()
        ys = self.get_ydata()
        zs = np.broadcast_to(zs, len(XS)) #-> why we have not self.get_zdata() ?
        self._verts3d = juggle_axes(xs, ys, zs, zdir)
        self.stale = True

Actual outcome

Traceback (most recent call last):
File "slider.py", line 318, in
plot_functions_3D(functions_list, colors_list)
File "slider.py", line 181, in plot_functions_3D
add_arrow_3d(line3d, d=10)
File "slider.py", line 88, in add_arrow_3d
zdata = line.get_zdata()
AttributeError: 'Line3D' object has no attribute 'get_zdata'

Expected outcome

the z value

Additional information

No response

Operating system

Mac OS

Matplotlib Version

Version: ImageMagick 7.1.1-6 Q16-HDRI x86_64 21020 https://imagemagick.org Copyright: (C) 1999 ImageMagick Studio LLC License: https://imagemagick.org/script/license.php Features: Cipher DPC HDRI Modules OpenMP(5.0) Delegates (built-in): bzlib fontconfig freetype gslib heic jng jp2 jpeg jxl lcms lqr ltdl lzma openexr png ps raw tiff webp xml zlib Compiler: gcc (4.2) Usage: import [options ...] [ file ]

Matplotlib Backend

No response

Python version

3.7

Jupyter version

No response

Installation

pip