Um ambiente virtual é um **diretório**, muito semelhante ao global, onde você pode instalar os pacotes para um projeto.

Dessa forma, cada projeto terá seu próprio ambiente virtual (diretório `.venv`) com seus próprios pacotes.

```mermaid
flowchart TB
    subgraph stone-project[philosophers-stone project]
        stone(philosophers-stone) --->|requires| harry-1
        subgraph venv1[.venv]

SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY

    }

    @Override public void proxySelectStart(Call call, HttpUrl url) {
      printEvent("proxySelectStart");
    }

    @Override public void proxySelectEnd(Call call, HttpUrl url, List<Proxy> proxies) {
      printEvent("proxySelectEnd");
    }

    @Override public void dnsStart(Call call, String domainName) {
      printEvent("dnsStart");
    }

     * @return requested (de-)activation(s) of profile(s) in this execution. Never {@code null}.
     */
    ProfileActivation getProfileActivation();

    // Proxies
    List<Proxy> getProxies();

    MavenExecutionRequest setProxies(List<Proxy> proxies);

    MavenExecutionRequest addProxy(Proxy proxy);

    // Servers
    List<Server> getServers();

///

```Python hl_lines="10"
{!> ../../docs_src/header_params/tutorial002.py!}
```

////

/// warning

Before setting `convert_underscores` to `False`, bear in mind that some HTTP proxies and servers disallow the usage of headers with underscores.

///

## Duplicate headers

It is possible to receive duplicate headers. That means, the same header with multiple values.

## Desenvolvimento

Quando comecei a criar o **FastAPI** de fato, a maior parte das peças já estavam encaixadas, o design estava definido, os requisitos e ferramentas já estavam prontos, e o conhecimento sobre os padrões e especificações estavam claros e frescos.

## Futuro

Nesse ponto, já está claro que o **FastAPI** com suas ideias está sendo útil para muitas pessoas.

    }

    @Override public void proxySelectStart(Call call, HttpUrl url) {
      printEvent("proxySelectStart");
    }

    @Override public void proxySelectEnd(Call call, HttpUrl url, List<Proxy> proxies) {
      printEvent("proxySelectEnd");
    }

    @Override public void callStart(Call call) {
      printEvent("callStart");
    }

    @Override public void dnsStart(Call call, String domainName) {

  protocols: List<Protocol>,
  connectionSpecs: List<ConnectionSpec>,
  /**
   * Returns this address's proxy selector. Only used if the proxy is null. If none of this
   * selector's proxies are reachable, a direct connection will be attempted.
   */
  @get:JvmName("proxySelector") val proxySelector: ProxySelector,
) {
  /**

and fitness for a particular purpose;

ii) effectively excludes on behalf of all Contributors all liability for damages,
including direct, indirect, special, incidental and consequential damages,
such as lost profits;

iii) states that any provisions which differ from this Agreement are offered
by that Contributor alone and not by any other party; and

iv) states that source code for the Program is available from such Contributor,

    override val call: Call,
    val url: HttpUrl,
  ) : CallEvent()

  data class ProxySelectEnd(
    override val timestampNs: Long,
    override val call: Call,
    val url: HttpUrl,
    val proxies: List<Proxy>?,
  ) : CallEvent() {
    override fun closes(event: CallEvent): Boolean = event is ProxySelectStart && call == event.call && url == event.url
  }

  data class DnsStart(
    override val timestampNs: Long,