how to pass folder path to custom function using MATLAB engine API for python

I have a funciton to load and process data in matlab, and I would like ot use it in python.

Using the matlab engine, I can call simple functions (standard and custom) that have input as double.

The problem is that when having the input a string(path folder), the funciton returns (0,0) and should be an array of many columns.

The Python code is below

Thanks in advance

import matlab.engine
import matlab
import numpy as np

eng = matlab.engine.start_matlab()


folder="D:\matlab results...."  # The folder path with text files to process
Amplitudes_all=eng.import_matlab_data(folder)  # function reads text files in selected folder and makes a 2D array with every file columnwise
ampsasarray=np.asarray(Amplitudes_all)

eng.quit()