When the `with` block finishes, it makes sure to close the file, even if there were exceptions.

When you create a dependency with `yield`, **FastAPI** will internally create a context manager for it, and combine it with some other related tools.

### Using context managers in dependencies with `yield` { #using-context-managers-in-dependencies-with-yield }

/// warning

This is, more or less, an "advanced" idea.

    @CanIgnoreReturnValue
    @Override
    public Builder<E> addAll(Iterator<? extends E> elements) {
      super.addAll(elements);
      return this;
    }

    @CanIgnoreReturnValue
    Builder<E> combine(Builder<E> other) {
      addAll(other.contents, other.size);
      return this;
    }

    /**
     * Returns a newly-created {@code ImmutableList} based on the contents of the {@code Builder}.
     */

 * The processor maintains a pool of searchers and an executor service for concurrent operations.
 * It implements rank fusion techniques to combine results from different search engines
 * and provides a unified search interface.
 */
public class RankFusionProcessor implements AutoCloseable {

    private static final Logger logger = LogManager.getLogger(RankFusionProcessor.class);

      for (Cell<? extends R, ? extends C, ? extends V> cell : table.cellSet()) {
        put(cell);
      }
      return this;
    }

    @CanIgnoreReturnValue
    Builder<R, C, V> combine(Builder<R, C, V> other) {
      this.cells.addAll(other.cells);
      return this;
    }

    /**
     * Returns a newly-created immutable table.
     *

                // Use AES-GCM - nonce is 16 bytes
                final Cipher cipher = createGCMCipher(false, nonce);
                cipher.updateAAD(associatedData);

                // Combine ciphertext and auth tag for decryption
                final byte[] input = new byte[ciphertext.length + authTag.length];
                System.arraycopy(ciphertext, 0, input, 0, ciphertext.length);

    }

    private byte[] calculateBindingInfo(ChannelInfo channel) {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();

        try {
            // Combine session key with channel-specific data
            byte[] sessionKey = getSessionKey();
            if (sessionKey != null) {
                baos.write(sessionKey);
            }

          <configuration>
            <source>1.8</source>
            <target>1.8</target>
            <encoding>UTF-8</encoding>
            <parameters>true</parameters>
            <compilerArgs combine.children="override">
              <!-- https://errorprone.info/docs/installation#maven -->
              <arg>-XDcompilePolicy=simple</arg>
              <arg>--should-stop=ifError=FLOW</arg>

          <configuration>
            <source>1.8</source>
            <target>1.8</target>
            <encoding>UTF-8</encoding>
            <parameters>true</parameters>
            <compilerArgs combine.children="override">
              <!-- https://errorprone.info/docs/installation#maven -->
              <arg>-XDcompilePolicy=simple</arg>
              <arg>--should-stop=ifError=FLOW</arg>

    public Builder<E> addAll(Iterator<? extends E> elements) {
      super.addAll(elements);
      return this;
    }

    @CanIgnoreReturnValue
    @Override
    Builder<E> combine(ImmutableSet.Builder<E> builder) {
      super.combine(builder);
      return this;
    }

    /**
     * Returns a newly-created {@code ImmutableSortedSet} based on the contents of the {@code
     * Builder} and its comparator.

    ImmutableRangeSet.Builder<Integer> zat =
        ImmutableRangeSet.<Integer>builder().add(rangeThree).add(rangeFour);

    ImmutableRangeSet<Integer> rangeSet = zis.combine(zat).build();

    assertThat(rangeSet.asRanges())
        .containsExactly(Range.closedOpen(1, 3), Range.closedOpen(4, 5), Range.closedOpen(6, 9))
        .inOrder();
  }