unsupported operand type(s) for -: 'str' and 'str' - Implementation LimeTabularExplainer - typeerror

Question

my issue is that I get the following error
enter image description here
when I try to follow the implementation given in the notebook
https://github.com/klemag/PyconUS_2019-model-interpretability-tutorial/blob/master/02-interpretability_LIME-solution.ipynb
by Kevin Lemagnen.
I have used his suggested way of preprocessing the data and converting them to the format needed by the LIME XAI technique.
I have used the following helper function:
`def convert_to_lime_format(X, categorical_names, col_names=None, invert=False):
"""Converts data with categorical values as string into the right format
for LIME, with categorical values as integers labels.
It takes categorical_names, the same dictionary that has to be passed
to LIME to ensure consistency.
col_names and invert allow to rebuild the original dataFrame from
a numpy array in LIME format to be passed to a Pipeline or sklearn
OneHotEncoder
"""
# If the data isn't a dataframe, we need to be able to build it
if not isinstance(X, pd.DataFrame):
X_lime = pd.DataFrame(X, columns=col_names)
else:
X_lime = X.copy()
for k, v in categorical_names.items():
if not invert:
label_map = {
str_label: int_label for int_label, str_label in enumerate(v)
}
else:
label_map = {
int_label: str_label for int_label, str_label in enumerate(v)
}
X_lime.iloc[:, k] = X_lime.iloc[:, k].map(label_map)
return X_lime`
How can I fix this issue? Any help would be greatly appreciated.
I have already looked around on Stackoverflow and I have googled the TypeError and I found the following explanation:
The python error TypeError: unsupported operand type(s) for -: ‘str’ and ‘str’ occurs when you try to subtract a string from another that contains numbers in both strings. The TypeError is due to the operand type minus (‘-‘) is unsupported between str (string). Auto casting is not supported by python. You can subtract a number from a different number. If you try to subtract a string from another string that may contain a number, the error TypeError: unsupported operand type(s) for -: ‘str’ and ‘str’ will be thrown.
In python, an arithmetic operation can be used between valid numbers. For example, you can subtract a number from a different number. The integer can be subtracted from a float number. If you try to subtract a string from a string that contains a number, the error TypeError: unsupported operand type(s) for -: ‘str’ and ‘str’ will be thrown.
Objects other than numbers can not be used in python substraction. The arithmetic subtract can be used only for numbers. If a number is stored as a string, it should be converted to an integer before subtracting it from each string. If you try to subtract a string to a string containing a number, the error TypeError: unsupported operand type(s) for +: ‘str’ and ‘str’ will be shown.
However, I was not able to resolve the problem.