mypy errors in test cases
c.f. https://github.com/adsharma/py2many/issues/358 for mypy errors in the transpiler.

The following is errors in the test cases.
```
tests/cases/global.py:17: error: Incompatible types in assignment (expression has type "str", variable has type "int")
tests/cases/fib_with_argparse.py:3: error: Cannot find implementation or library stub for module named 'argparse_dataclass'
tests/cases/fib_with_argparse.py:3: note: See https://mypy.readthedocs.io/en/latest/running_mypy.html#missing-imports
tests/cases/fib_with_argparse.py:19: error: "Type[Options]" has no attribute "parse_args"
tests/cases/sealed.py:3: error: Cannot find implementation or library stub for module named 'adt'
tests/cases/sealed.py:19: error: "int" not callable
tests/cases/sealed.py:23: error: "Packet" not callable
tests/cases/infer_ops.py:33: error: Unsupported left operand type for + ("c_int8")
tests/cases/infer_ops.py:37: error: Unsupported left operand type for + ("c_int16")
tests/cases/infer_ops.py:41: error: Unsupported left operand type for + ("c_int32")
tests/cases/infer_ops.py:45: error: Unsupported left operand type for + ("c_int64")
tests/cases/infer_ops.py:49: error: Unsupported left operand type for + ("c_uint8")
tests/cases/infer_ops.py:53: error: Unsupported left operand type for + ("c_uint16")
tests/cases/infer_ops.py:57: error: Unsupported left operand type for + ("c_uint32")
tests/cases/infer_ops.py:61: error: Unsupported left operand type for + ("c_uint64")
tests/cases/infer_ops.py:65: error: Unsupported left operand type for + ("c_int8")
tests/cases/infer_ops.py:69: error: Unsupported left operand type for - ("c_int8")
tests/cases/infer_ops.py:73: error: Unsupported left operand type for * ("c_int8")
tests/cases/infer_ops.py:77: error: Unsupported operand types for + ("c_int8" and "float")
tests/ext_cases/string_sum.py:7: error: Unsupported left operand type for + ("c_int8")
```

And I am guessing that the [`TYPE_ERROR_CASES`](https://github.com/adsharma/py2many/blob/main/tests/test_unsupported.py#L162) will also fail mypy.

global.py is an easy fix, avoiding reusing the `i` in the second loop.
