The function seems to insert the letter 'i' after the first non-numeric character present in the input string, and removes any digits after the inserted 'i'.

[CODE]:
```python
def f(x):
    result = []
    for char in x:
        if not char.isdigit():
            result.append(char)
            result.append('i')
            break
        else:
            result.append(char)
    return "".join(result)
```

Now, I'll test f(x) on a few more input strings to check if the description and code are accurate.

COMMAND: PYTHON(./temp/function.py example 87fun num9ber)