assertThat(transformation.inverse().inverse()).isSameInstanceAs(transformation);
  }

  /**
   * Asserts that {@code transformation} behaves as expected for {@link
   * LinearTransformation#forNaN}.
   */
  static void assertLinearTransformationNaN(LinearTransformation transformation) {
    assertThat(transformation.isHorizontal()).isFalse();

/**
 * Standard transformer implementation for the Fess search engine.
 * This transformer handles document transformation and content extraction using
 * the standard Fess file transformation process with support for various content types.
 *
 * <p>It extends AbstractFessFileTransformer to provide file-specific transformation
 * capabilities while using the appropriate extractor for each document type.</p>
 */

   * vertical transformation (i.e. when {@link #isVertical()} is true).
   */
  public abstract double transform(double x);

  /**
   * Returns the inverse linear transformation. The inverse of a horizontal transformation is a
   * vertical transformation, and vice versa. The inverse of the {@link #forNaN} transformation is

    LinearTransformation transformation = LinearTransformation.mapping(x1, y1).withSlope(slope);
    assertThat(transformation.isVertical()).isFalse();
    assertThat(transformation.isHorizontal()).isFalse();
    assertThat(transformation.slope()).isWithin(ALLOWED_ERROR).of(slope);
    // Note that we cannot test the actual mapping of points, as the results will be unreliable due
    // to loss of precision with this value of the slope.
  }

    LinearTransformation transformation = LinearTransformation.mapping(x1, y1).withSlope(slope);
    assertThat(transformation.isVertical()).isFalse();
    assertThat(transformation.isHorizontal()).isFalse();
    assertThat(transformation.slope()).isWithin(ALLOWED_ERROR).of(slope);
    // Note that we cannot test the actual mapping of points, as the results will be unreliable due
    // to loss of precision with this value of the slope.
  }

    assertThat(transformation.inverse().inverse()).isSameInstanceAs(transformation);
  }

  /**
   * Asserts that {@code transformation} behaves as expected for {@link
   * LinearTransformation#forNaN}.
   */
  static void assertLinearTransformationNaN(LinearTransformation transformation) {
    assertThat(transformation.isHorizontal()).isFalse();

  /**
   * UTF-8: eight-bit UCS Transformation Format.
   *
   * @deprecated Use {@link StandardCharsets#UTF_8} instead.
   */
  @Deprecated public static final Charset UTF_8 = StandardCharsets.UTF_8;

  /**
   * UTF-16BE: sixteen-bit UCS Transformation Format, big-endian byte order.
   *
   * @deprecated Use {@link StandardCharsets#UTF_16BE} instead.
   */

  /**
   * UTF-8: eight-bit UCS Transformation Format.
   *
   * @deprecated Use {@link StandardCharsets#UTF_8} instead.
   */
  @Deprecated public static final Charset UTF_8 = StandardCharsets.UTF_8;

  /**
   * UTF-16BE: sixteen-bit UCS Transformation Format, big-endian byte order.
   *
   * @deprecated Use {@link StandardCharsets#UTF_16BE} instead.
   */

    }

    /**
     * Returns the transformation.
     *
     * @return the transformation
     */
    public String getTransformation() {
        return transformation;
    }

    /**
     * Sets the transformation.
     *
     * @param transformation
     *            the transformation
     */
    public void setTransformation(final String transformation) {

import jakarta.annotation.PostConstruct;

/**
 * File transformer implementation for the Fess search engine.
 * This transformer handles file-based document transformation and content extraction
 * using the Fess file transformation process with support for various file types.
 *
 * <p>It extends AbstractFessFileTransformer to provide specialized file processing