Pass key-value pairs into Struct constructor in python

What language does this apply to?
python

Describe the problem you are trying to solve.
When we initialise a Struct and want to set key-value pair on the struct, there are two steps:

struct = Struct()
struct.update(key1='value-1', key2=2)

Alternatively, we can also use json_format.ParseDict.

Describe the solution you'd like
Hopefully, we can do the following:

struct = Struct(fields={'key1': 'value-1, 'key2: 2})
# or 
struct = Struct({'key1': 'value-1, 'key2: 2})

Describe alternatives you've considered

Additional context
Add any other context or screenshots about the feature request here.

Start in python/google/protobuf/internal/well_known_types.py at the Struct implementation linked in the issue, and compare its current construction and update behavior. Implement the requested key-value initialization while preserving the existing update path; done means the documented mapping or keyword forms work as shown.