Addpattern with mypy - name already defined

I was going throught the case studies for `coconut` tutorial and tried using `addpattern`

```python
def factorial(0) = 1

addpattern def factorial(n is int if n > 0) =
"""Compute n! where n is an integer >= 0."""
n * factorial(n - 1)

# Test cases:
-1 |> factorial |> print # MatchError
0.5 |> factorial |> print # MatchError
0 |> factorial |> print # 1
3 |> factorial |> print # 6
```

Now compiling with `coconut fact.coco --mypy` yielded

```
CoconutWarning: missing __init__.coco in package: '...'
Compiling fact.coco ...
Compiled to fact.py .
fact.py:39: error: Name 'factorial' already defined on line 23
Found 1 error in 1 file (checked 1 source file)
Exiting due to MyPy error.
```

The code runs and all but I want to know if this is expected and desired output from `mypy`?

Start by compiling the shown fact.coco example with --mypy and inspect the generated fact.py around the two factorial definitions. Determine whether the duplicate-name diagnostic is expected for addpattern output; done means the behavior is confirmed and documented or the compiler and its relevant coverage are updated if it is incorrect.

Written by the indexing model from the issue text.