In types.Attributes, change Dict -> Mapping

[aabmass]

Description

Fixes these kinds of type errors which I'm seeing in the Google cloud exporter:

def usesAttributes(a: types.Attributes) -> None:
    pass

foo: Dict[str, str] = {"key": "value"}

# Causes type error:
# has incompatible type "Dict[str, str]"; expected
# "Optional[Dict[str, Union[str, bool, int, float, Sequence[str], Sequence[bool], Sequence[int], Sequence[float]]]]
usesAttributes(foo)

• This happens because Dict is invariant (see this mypy FAQ). Using Mapping solves this because it is covariant.
• This also has the benefit that Mapping is immutable so MyPy will complain if you try and set a value on it.

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

For GoogleCloudPlatform/opentelemetry-operations-python#64

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

This is just a type annotation change. All mypy assertions are passing

• MyPy tox env

Checklist:

(rest are N/A)

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[codeboten]

Nice!