}

  @LazyInit private transient @Nullable ColumnMap columnMap;

  @Override
  public Map<C, Map<R, @Nullable V>> columnMap() {
    ColumnMap map = columnMap;
    return (map == null) ? columnMap = new ColumnMap() : map;
  }

  @WeakOuter
  private final class ColumnMap extends ArrayMap<C, Map<R, @Nullable V>> {
    private ColumnMap() {
      super(columnKeyToIndex);
    }

    @Override

      return Maps.transformValues(fromTable.rowMap(), row -> Maps.transformValues(row, function));
    }

    @Override
    public Map<C, Map<R, V2>> columnMap() {
      return Maps.transformValues(
          fromTable.columnMap(), column -> Maps.transformValues(column, function));
    }
  }

  /**
   * Returns an unmodifiable view of the specified table. This method allows modules to provide

  }

  @LazyInit private transient @Nullable ColumnMap columnMap;

  @Override
  public Map<C, Map<R, @Nullable V>> columnMap() {
    ColumnMap map = columnMap;
    return (map == null) ? columnMap = new ColumnMap() : map;
  }

  @WeakOuter
  private final class ColumnMap extends ArrayMap<C, Map<R, @Nullable V>> {
    private ColumnMap() {
      super(columnKeyToIndex);
    }

    @Override

  public ImmutableMap<R, V> column(C columnKey) {
    checkNotNull(columnKey, "columnKey");
    return MoreObjects.firstNonNull(
        (ImmutableMap<R, V>) columnMap().get(columnKey), ImmutableMap.of());
  }

  @Override
  public ImmutableSet<C> columnKeySet() {
    return columnMap().keySet();
  }

  /**
   * {@inheritDoc}
   *

   *
   * <p>In contrast, the maps returned by {@code columnMap().get()} have the same behavior as those
   * returned by {@link #column}. Those maps may support {@code setValue()}, {@code put()}, and
   * {@code putAll()}.
   *
   * @return a map view from each column key to a secondary map from row keys to values
   */
  Map<C, Map<R, V>> columnMap();

  /**

  public ImmutableMap<R, V> column(C columnKey) {
    checkNotNull(columnKey, "columnKey");
    return MoreObjects.firstNonNull(
        (ImmutableMap<R, V>) columnMap().get(columnKey), ImmutableMap.of());
  }

  @Override
  public ImmutableSet<C> columnKeySet() {
    return columnMap().keySet();
  }

  /**
   * {@inheritDoc}
   *

   *
   * <p>In contrast, the maps returned by {@code columnMap().get()} have the same behavior as those
   * returned by {@link #column}. Those maps may support {@code setValue()}, {@code put()}, and
   * {@code putAll()}.
   *
   * @return a map view from each column key to a secondary map from row keys to values
   */
  Map<C, Map<R, V>> columnMap();

  /**

      table.put(1, "foo", 'a');
      table.put(1, "bar", 'b');
      table.put(3, "foo", 'c');
      return table.columnMap();
    }

    @Override
    protected Map<String, Map<Integer, Character>> makeEmptyMap() {
      return makeTable().columnMap();
    }
  }

entiende que la base de datos proporcionará el `id` y *define la columna como un `INTEGER` no nulo* en el esquema de la base de datos. Consulta la <a href="https://sqlmodel.tiangolo.com/tutorial/create-db-and-table/#primary-key-id" class="external-link" target="_blank">documentación de SQLModel sobre claves primarias</a> para más detalles.

* `Field(index=True)` le dice a SQLModel que debe crear un **índice SQL** para esta columna, lo que permitirá búsquedas más rápidas en la base de datos cuando...

## Ejecución de dependencias con `yield` { #execution-of-dependencies-with-yield }

La secuencia de ejecución es más o menos como este diagrama. El tiempo fluye de arriba a abajo. Y cada columna es una de las partes que interactúa o ejecuta código.

```mermaid
sequenceDiagram

participant client as Client
participant handler as Exception handler
participant dep as Dep with yield