AssertionError in scanpy.read_10x_mtx

`AssertionError` in `scanpy.read_10x_mtx` usually occurs when there is an issue with the format of the input data. Here are a few things you can try to resolve the issue:

1. Make sure that you are passing the correct path to the input data. Check for any typos or missing file extensions.

2. Check the format of the input data. `scanpy.read_10x_mtx` expects input data in the 10x Genomics format, so make sure that your data is formatted correctly.

3. Check the version of the `scanpy` package you are using. If you are using an outdated version, try upgrading to the latest version.

4. If none of the above solutions work, you can try using an alternative method to read in your data. For example, you can try using the `read_mtx` function in the `scipy.io` module to read in your data.