Incorrect Serialization Format for defaultDuration in BookingService

Describe the bug

The defaultDuration field in the BookingService model is being serialized incorrectly due to the behavior of the write_timedelta_value method in the json_serialization_writer.py module.

According to the Microsoft Graph API documentation for BookingService, the defaultDuration field must be serialized as an ISO 8601 duration, e.g., P11D23H59M59.999999999999S.

However, the SDK currently serializes Python timedelta objects using the default str(timedelta) representation, which does not conform to ISO 8601. This results in requests being sent with incorrectly formatted durations and leading to 400 Graph API errors.

Relevant Code:

File: msgraph/generated/models/booking_service.py

writer.write_timedelta_value("defaultDuration", self.default_duration)

File: kiota_serialization_json/json_serialization_writer.py

def write_timedelta_value(self, key: Optional[str], value: Optional[timedelta]) -> None:
    if isinstance(value, timedelta):
        if key:
            self.writer[key] = str(value)  # <-- Incorrect format
        else:
            self.value = str(value)

Expected behavior

write_timedelta_value should serialize timedelta objects to valid ISO 8601 duration strings (e.g., P1DT2H3M4S), not the default str(timedelta) representation (1 day, 2:03:04).

How to reproduce

Create a BookingService object with a default_duration = timedelta(days=1, hours=2, minutes=3, seconds=4).

Serialize the object.

Observe that the serialized value for defaultDuration is "1 day, 2:03:04" instead of "P1DT2H3M4S".

SDK Version

1.33.0

Latest version known to work for scenario above?

No response

Known Workarounds

Currently manually patching the serialize method to use correct serialization

from datetime import timedelta

from isodate import duration_isoformat
from kiota_abstractions.serialization.serialization_writer import SerializationWriter
from msgraph.generated.models.booking_service import BookingService


def patch_booking_service(booking_service: BookingService) -> None:
    old_serializer = booking_service.serialize

    def booking_service_serializer_patch(writer: SerializationWriter) -> None:
        old_serializer(writer)
        if isinstance(booking_service.default_duration, timedelta):
            writer.writer["defaultDuration"] = duration_isoformat(booking_service.default_duration) 

    booking_service.serialize = booking_service_serializer_patch 

Debug output

Configuration

SDK Version: Latest (as of writing)

Python Version: 3.11+

Endpoint: /solutions/bookingBusinesses/{id}/services

Other information

Proposed Fix
Add a new utility function for ISO 8601 serialization
File: kiota_serialization_json/json_serialization_writer.py:

from isodate import duration_isoformat

def write_iso8601_duration(self, key: Optional[str], value: Optional[timedelta]) -> None:
    """
    Writes a timedelta as an ISO 8601 duration string (e.g., P1DT2H3M4S).
    """
    if isinstance(value, timedelta):
        duration = duration_isoformat(value)
        if key:
            self.writer[key] = duration
        else:
            self.value = duration

Then update BookingService to call this new method explicitly:

File: msgraph/generated/models/booking_service.py:

@dataclass
class BookingService(Entity, Parsable):
    ...
    def serialize(self, writer: SerializationWriter) -> None:
        ...
        # Use the custom method for ISO 8601 durations
        if hasattr(writer, "write_iso8601_duration"):
            writer.write_iso8601_duration("defaultDuration", self.default_duration)
        else:
            writer.write_timedelta_value("defaultDuration", self.default_duration)  # Fallback