The to_dict method creates invalid output. It uses mangled field names instead of the original proto field names.

[Ark-kun]

Code:

from google.cloud.aiplatform_v1 import Citation
Citation.to_dict(Citation())

                 {
                   "start_index": 0,
                   "end_index": 0,
                   "uri": "",
                   "title": "",
                   "license_": ""
                 }

Notice how the dictionary uses license_ instead of license.

Proto:
https://github.com/googleapis/googleapis/blob/0179dcc4d2b4d7376e7f0292b15c72aab3100dd6/google/cloud/aiplatform/v1beta1/content.proto#L295

The correct proto field name is license.

// Source attributions for content.
message Citation {
  // Output only. Start index into the content.
  int32 start_index = 1 [(google.api.field_behavior) = OUTPUT_ONLY];

  // Output only. End index into the content.
  int32 end_index = 2 [(google.api.field_behavior) = OUTPUT_ONLY];

  // Output only. Url reference of the attribution.
  string uri = 3 [(google.api.field_behavior) = OUTPUT_ONLY];

  // Output only. Title of the attribution.
  string title = 4 [(google.api.field_behavior) = OUTPUT_ONLY];

  // Output only. License of the attribution.
  string license = 5 [(google.api.field_behavior) = OUTPUT_ONLY];

  // Output only. Publication date of the attribution.
  google.type.Date publication_date = 6
      [(google.api.field_behavior) = OUTPUT_ONLY];
}

Generated class:
https://github.com/googleapis/python-aiplatform/blob/c56dd50310ecc42d6a3b0cd2f30db71e8cad0cf6/google/cloud/aiplatform_v1/types/content.py#L536C1-L581C1

class Citation(proto.Message):
    r"""Source attributions for content.

    Attributes:
        start_index (int):
            Output only. Start index into the content.
        end_index (int):
            Output only. End index into the content.
        uri (str):
            Output only. Url reference of the
            attribution.
        title (str):
            Output only. Title of the attribution.
        license_ (str):
            Output only. License of the attribution.
        publication_date (google.type.date_pb2.Date):
            Output only. Publication date of the
            attribution.
    """

    start_index: int = proto.Field(
        proto.INT32,
        number=1,
    )
    end_index: int = proto.Field(
        proto.INT32,
        number=2,
    )
    uri: str = proto.Field(
        proto.STRING,
        number=3,
    )
    title: str = proto.Field(
        proto.STRING,
        number=4,
    )
    license_: str = proto.Field(
        proto.STRING,
        number=5,
    )
    publication_date: date_pb2.Date = proto.Field(
        proto.MESSAGE,
        number=6,
        message=date_pb2.Date,
    )