app = FastAPI()
    model = ModelWithDatetimeField(dt_field=datetime(2019, 1, 1, 8))

    @app.get("/model", response_model=ModelWithDatetimeField)
    def get_model():
        return model

    client = TestClient(app)
    with client:
        response = client.get("/model")

Use base64 only if you definitely need to include binary data in JSON, and you can't use files for that.

## Pydantic `bytes` { #pydantic-bytes }

You can declare a Pydantic model with `bytes` fields, and then use `val_json_bytes` in the model config to tell it to use base64 to *validate* input JSON data, as part of that validation it will decode the base64 string into bytes.

 */
package org.apache.maven.model.building;

/**
 * Collects problems that are encountered during model building. The primary purpose of this component is to account for
 * the fact that the problem reporter has/should not have information about the calling context and hence cannot provide
 * an expressive source hint for the model problem. Instead, the source hint is configured by the model builder before

 * under the License.
 */
package org.apache.maven.model.profile.activation;

import javax.inject.Named;
import javax.inject.Singleton;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.regex.Pattern;

import org.apache.maven.model.Activation;
import org.apache.maven.model.Profile;
import org.apache.maven.model.building.ModelProblem.Severity;

          "language-java",
          "language-jvm",
          "language-native",
          "launcher",
          "logging",
          "maven",
          "messaging",
          "model-core",
          "model-groovy",
          "persistent-cache",
          "platform-base",
          "platform-jvm",
          "platform-native",
          "plugin-development",
          "plugin-use",

 * under the License.
 */
package org.apache.maven.model.building;

import org.apache.maven.building.StringSource;

/**
 * Wraps an ordinary {@link CharSequence} as a model source.
 *
 *
 * @deprecated instead use {@link StringSource}
 */
@Deprecated
public class StringModelSource extends StringSource implements ModelSource {

    /**
     * Creates a new model source backed by the specified string.
     *

app = FastAPI()


class Model(BaseModel):
    param: str

    model_config = {"extra": "allow"}


@app.get("/query")
async def query_model_with_extra(data: Model = Query()):
    return data


@app.get("/header")
async def header_model_with_extra(data: Model = Header()):
    return data


@app.get("/cookie")
async def cookies_model_with_extra(data: Model = Cookie()):
    return data

 * @see Source
 */
public interface ModelSource extends Source {

    /**
     * Returns the model identifier in the format {@code groupId:artifactId:version}
     * if this source represents a resolved artifact with known coordinates.
     * <p>
     * This method is primarily used by resolved sources to provide the model ID
     * without requiring the XML to be parsed. For build sources, this typically

 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.toolchain;

import java.io.File;

import org.apache.maven.toolchain.model.PersistedToolchains;

/**
 * Builds the toolchains model from a previously configured filesystem path to the toolchains file.
 * <strong>Note:</strong> This is an internal component whose interface can change without prior notice.
 *

```mermaid
graph TB
    subgraph "❌ Not Supported"
        direction TB
        subgraph V2["Pydantic v2 Model"]
            V1Field["Pydantic v1 Model"]
        end
        subgraph V1["Pydantic v1 Model"]
            V2Field["Pydantic v2 Model"]
        end
    end

    style V2 fill:#f9fff3
    style V1 fill:#fff6f0
    style V1Field fill:#fff6f0
    style V2Field fill:#f9fff3