# Using Dataclasses { #using-dataclasses }

FastAPI is built on top of **Pydantic**, and I have been showing you how to use Pydantic models to declare requests and responses.

But FastAPI also supports using <a href="https://docs.python.org/3/library/dataclasses.html" class="external-link" target="_blank">`dataclasses`</a> the same way:

{* ../../docs_src/dataclasses/tutorial001.py hl[1,7:12,19:20] *}

        verify(mockNdrBuffer, times(1)).enc_ndr_small(100);
        verifyNoMoreInteractions(mockNdrBuffer);
    }

    @Test
    void testDecode() throws NdrException {
        // Define the value that dec_ndr_small should return
        int decodedValue = 200;
        when(mockNdrBuffer.dec_ndr_small()).thenReturn(decodedValue);

        // Create an NdrSmall object (initial value doesn't matter for decode)

If you use any other tool to manage your installations, like `uv`, Poetry, Pipenv, or others, they all have a way that you can use to define specific versions for your packages.

## Available versions { #available-versions }

import org.apache.maven.api.di.Named;

/**
 * Service provider interface for registering custom {@link Language} implementations.
 * <p>
 * This interface allows plugins and extensions to define and register additional programming languages
 * beyond the standard ones provided by Maven. Implementations of this interface will be discovered
 * through the Java ServiceLoader mechanism and their provided languages will be available

 * }
 *
 * <p>Graph algorithms that need additional capabilities (accessing both predecessors and
 * successors, iterating over the edges, etc.) should declare their input to be of a type that
 * provides those capabilities, such as {@link Graph}, {@link ValueGraph}, or {@link Network}.
 *
 * <h3>Additional documentation</h3>
 *

 * }
 *
 * <p>Graph algorithms that need additional capabilities (accessing both predecessors and
 * successors, iterating over the edges, etc.) should declare their input to be of a type that
 * provides those capabilities, such as {@link Graph}, {@link ValueGraph}, or {@link Network}.
 *
 * <h3>Additional documentation</h3>
 *

/*!
 * clipboard.js v2.0.11
 * https://clipboardjs.com/
 *
 * Licensed MIT © Zeno Rocha
 */

I'll tell you a bit more about these **concepts** here, and that would hopefully give you the **intuition** you would need to decide how to deploy your API in very different environments, possibly even in **future** ones that don't exist yet.

By considering these concepts, you will be able to **evaluate and design** the best way to deploy **your own APIs**.

import org.apache.maven.api.annotations.Experimental;
import org.apache.maven.api.annotations.ThreadSafe;

/**
 * Represents the contract for Mojos to interact with the Maven infrastructure.
 * Implementations of this interface define specific build-process behaviors
 * that are triggered during a Maven build lifecycle.
 *
 * The primary entry point is the {@link #execute()} method, which encapsulates

   |
   | * provides: A list of key/value-pairs.
   |   Based on the toolchain-configuration in the pom.xml Maven will search for
   |   matching <provides/> configuration. You can decide for yourself which key-value
   |   pairs to use. Often used keys are 'version', 'vendor' and 'arch'. By default
   |   the version has a special meaning. If you configured in the pom.xml '1.5'