I'm following the documentation of Django, and I've encountered a problem running this command: 
 python manage.py shell

This is the error I get:

```
File "manage.py", line 7
  from django.core.management import execute_from_command_line

TabError: inconsistent use of tabs and space in indentation

```

I realize what it means, but I don't know how to edit my manage.py file so it works. I might have accidentally edited the indentations and now I don't know how to revert.

This is what my manage.py file currently looks like:

```
#!/usr/bin/env python
import os
import sys

if __name__ == "__main__":
    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "polling.settings")
    from django.core.management import execute_from_command_line
    execute_from_command_line(sys.argv)

```

Thanks!