np.save() works with a reproducible example but not with my data.
How can I save my numpy array as binary?

np.save works in this reproducible example:

a = np.arange(12, dtype='float32').reshape(2,2,3)
a.shape
Out[42]: (2, 2, 3)
a.dtype
Out[43]: dtype('float32')
np.save("delme",a)

But not with my numpy array variable_data:

variable_data.shape
Out[45]: (3500, 480, 640)
variable_data.dtype
Out[46]: dtype('float32')
ma.is_masked(variable_data)
Out[52]: False

Then, I get an error:

np.save("delme2", variable_data)
---------------------------------------------------------------------------
NotImplementedError                       Traceback (most recent call last)
Cell In[41], line 3
      1 variable_data.shape
      2 variable_data.dtype
----> 3 np.save("delme2", variable_data)

File ~/miniforge3/envs/sediment/lib/python3.9/site-packages/numpy/lib/npyio.py:546, in save(file, arr, allow_pickle, fix_imports)
    544 with file_ctx as fid:
    545     arr = np.asanyarray(arr)
--> 546     format.write_array(fid, arr, allow_pickle=allow_pickle,
    547                        pickle_kwargs=dict(fix_imports=fix_imports))

File ~/miniforge3/envs/sediment/lib/python3.9/site-packages/numpy/lib/format.py:730, in write_array(fp, array, version, allow_pickle, pickle_kwargs)
    728 else:
    729     if isfileobj(fp):
--> 730         array.tofile(fp)
    731     else:
    732         for chunk in numpy.nditer(
    733                 array, flags=['external_loop', 'buffered', 'zerosize_ok'],
    734                 buffersize=buffersize, order='C'):

File ~/miniforge3/envs/sediment/lib/python3.9/site-packages/numpy/ma/core.py:6221, in MaskedArray.tofile(self, fid, sep, format)
   6208 def tofile(self, fid, sep="", format="%s"):
   6209     """
   6210     Save a masked array to a file in binary format.
   6211 
   (...)
   6219 
   6220     """
-> 6221     raise NotImplementedError("MaskedArray.tofile() not implemented yet.")

NotImplementedError: MaskedArray.tofile() not implemented yet.