## Duplicate headers { #duplicate-headers }

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

You can define those cases using a list in the type declaration.

You will receive all the values from the duplicate header as a Python `list`.

For example, to declare a header of `X-Token` that can appear more than once, you can write:

{* ../../docs_src/header_params/tutorial003_an_py310.py hl[9] *}

pkg go/doc/comment, type LinkDef struct, URL string #51082
pkg go/doc/comment, type LinkDef struct, Used bool #51082
pkg go/doc/comment, type List struct #51082
pkg go/doc/comment, type List struct, ForceBlankBefore bool #51082
pkg go/doc/comment, type List struct, ForceBlankBetween bool #51082
pkg go/doc/comment, type List struct, Items []*ListItem #51082
pkg go/doc/comment, type ListItem struct #51082

    INSTANCE;

    static <V extends @Nullable Object> Supplier<List<V>> instance() {
      // Each call generates a fresh LinkedList, which can serve as a List<V> for any V.
      @SuppressWarnings({"rawtypes", "unchecked"})
      Supplier<List<V>> result = (Supplier) INSTANCE;
      return result;
    }

    @Override

    INSTANCE;

    static <V extends @Nullable Object> Supplier<List<V>> instance() {
      // Each call generates a fresh LinkedList, which can serve as a List<V> for any V.
      @SuppressWarnings({"rawtypes", "unchecked"})
      Supplier<List<V>> result = (Supplier) INSTANCE;
      return result;
    }

    @Override

                                </la:form>
                            </div>
                            <%-- List --%>
                            <c:if test="${boostDocPager.allRecordCount == 0}">
                                <div class="row top10"><div class="col-sm-12 empty-list-placeholder"><i class="fa fa-info-circle text-primary" aria-hidden="true"></i>

 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.repository.legacy.resolver.transform;

import java.util.List;

import org.apache.maven.artifact.Artifact;
import org.apache.maven.artifact.deployer.ArtifactDeploymentException;
import org.apache.maven.artifact.installer.ArtifactInstallationException;

                                </la:form>
                            </div>
                            <%-- List --%>
                            <c:if test="${fileConfigPager.allRecordCount == 0}">
                                <div class="row top10"><div class="col-sm-12 empty-list-placeholder"><i class="fa fa-info-circle text-primary" aria-hidden="true"></i>

                if (line.length() > 0 && !line.startsWith("#")) {
                    list.add(line.trim());
                }
            }
        } catch (final Exception e) {
            throw new SuggestSettingsException("Failed to load default badwords.", e);
        }
        defaultWords = list.toArray(new String[list.size()]);
    }

import com.google.common.util.concurrent.ListenableScheduledFuture;
import com.google.common.util.concurrent.ListeningScheduledExecutorService;
import com.google.common.util.concurrent.MoreExecutors;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.Delayed;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;

 * under the License.
 */
package org.apache.maven.lifecycle;

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

import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.apache.maven.execution.MavenSession;
import org.apache.maven.lifecycle.internal.LifecycleExecutionPlanCalculator;