can only concatenate str (not "dict") to str

This error occurs when you try to concatenate a string with a dictionary in Python. In Python, the `+` operator can only be used to concatenate two strings. If you want to combine a dictionary with a string, you need to convert the dictionary to a string first. Here's an example:

my_dict = {'key': 'value'}
my_string = 'The dictionary is: ' + str(my_dict)
print(my_string)

This will convert the dictionary `my_dict` to a string using the `str()` function and then concatenate it with the string `'The dictionary is: '`. The output will be `'The dictionary is: {'key': 'value'}`.