I get ModuleNotFoundError when I try setting a custom preprocessor to my settings.py file

[ssebastian90]

I try to set a custom preprocessor "custom_lowercase_preprocessor" from module "custom_preprocessors" that is located in the same directory with the settingspy file and I get a ModuleNotFoundError No module named 'custom_preprocessors'.
Could anyone help with some pointers for I can't see where the problem is .

This is my full Chatterbot settings.

CHATTERBOT = {
'name': 'Chatbot',
'django_app_name': 'django_chatterbot',
'preprocessors': [
'chatterbot.preprocessors.clean_whitespace',
'custom_preprocessors.custom_lowercase_preprocessor',
],
'logic_adapters': [
{
'import_path': 'chatterbot.logic.BestMatch',
'default_response': 'Sorry but I have no answer.',
'maximum_similarity_threshold': 0.00,
'statement_comparison_function': LevenshteinDistance,
},
'chatterbot.logic.TimeLogicAdapter',
],
}