The function removes spaces from the input string and returns the modified string without any spaces.

[CODE]: 
```python
def remove_spaces(input_string):
    return input_string.replace(" ", "")
```
Now, let's try one more test with inputs that contain only spaces or mixed with characters.

COMMAND: PYTHON(./temp/function.py "spaces   " "   mixed  with spaces" "all  spaces  ")