}

  /** Returns whether this is a vertical transformation. */
  public abstract boolean isVertical();

  /** Returns whether this is a horizontal transformation. */
  public abstract boolean isHorizontal();

  /**
   * Returns the slope of the transformation, i.e. the rate of change of {@code y} with respect to
   * {@code x}. This must not be called on a vertical transformation (i.e. when {@link

-item-text{display:block;padding:.25rem 1.5rem;color:#212529}.btn-group,.btn-group-vertical{position:relative;display:-ms-inline-flexbox;display:inline-flex;vertical-align:middle}.btn-group-vertical>.btn,.btn-group>.btn{position:relative;-ms-flex:1 1 auto;flex:1 1 auto}.btn-group-vertical>.btn:hover,.btn-group>.btn:hover{z-index:1}.btn-group-vertical>.btn.active,.btn-group-vertical>.btn:active,.btn-group-vertical>.btn:focus,.btn-group>.btn.active,.btn-group>.btn:active,.btn-group>.btn:focus{z-in...

isabled-color:#adb5bd;--bs-dropdown-header-color:#adb5bd}.btn-group,.btn-group-vertical{position:relative;display:inline-flex;vertical-align:middle}.btn-group-vertical>.btn,.btn-group>.btn{position:relative;flex:1 1 auto}.btn-group-vertical>.btn-check:checked+.btn,.btn-group-vertical>.btn-check:focus+.btn,.btn-group-vertical>.btn.active,.btn-group-vertical>.btn:active,.btn-group-vertical>.btn:focus,.btn-group-vertical>.btn:hover,.btn-group>.btn-check:checked+.btn,.btn-group>.btn-check:focus+.btn...

}

a[data-external-link]:not(:has(img)):not(.no-link-icon):not(.announce-link)::after {
  content: "";
  display: inline-block;
  width: 0.75em;
  height: 0.75em;
  margin-left: 0.25em;
  vertical-align: middle;
  opacity: 0.55;
  background: currentColor;

}

[data-ty] {
    display: block;
    line-height: 2;
}

[data-ty]:before {
    /* Set up defaults and ensure empty lines are displayed. */
    content: '';
    display: inline-block;
    vertical-align: middle;
}

[data-ty="input"]:before,
[data-ty-prompt]:before {
    margin-right: 0.75em;
    color: var(--color-text-subtle);
}

[data-ty="input"]:before {
    content: '$';
}

  transform: rotate(135deg);
  -webkit-transform: rotate(135deg);
}

.daterangepicker .calendar-table th, .daterangepicker .calendar-table td {
  white-space: nowrap;
  text-align: center;
  vertical-align: middle;
  min-width: 32px;
  width: 32px;
  height: 24px;
  line-height: 24px;
  font-size: 12px;
  border-radius: 4px;
  border: 1px solid transparent;
  white-space: nowrap;

## Using `Union` or `Optional` { #using-union-or-optional }

If your code for some reason can't use `|`, for example if it's not in a type annotation but in something like `response_model=`, instead of using the vertical bar (`|`) you can use `Union` from `typing`.

For example, you could declare that something could be a `str` or `None`:

```python
from typing import Union


def say_hi(name: Union[str, None]):

   * xStats().populationVariance() > 0.0 || yStats().populationVariance() > 0.0}). The result is
   * guaranteed to be horizontal if there is variance in the {@code x} data but not the {@code y}
   * data, and vertical if there is variance in the {@code y} data but not the {@code x} data.
   *
   * <p>This fit minimizes the root-mean-square error in {@code y} as a function of {@code x}. This

    checkArgument(xDelta != 0.0);
    checkArgument(yDelta != 0.0);
    assertThat(transformation.isHorizontal()).isFalse();
    assertThat(transformation.isVertical()).isFalse();
    assertThat(transformation.inverse().isHorizontal()).isFalse();
    assertThat(transformation.inverse().isVertical()).isFalse();
    assertThat(transformation.transform(x1)).isWithin(ALLOWED_ERROR).of(y1);

    }

    /** WAVE DASH */
    public static final char WAVE_DASH = '\u301C';

    /** FULLWIDTH TILDE */
    public static final char FULLWIDTH_TILDE = '\uFF5E';

    /** DOUBLE VERTICAL LINE */
    public static final char DOUBLE_VERTICAL_LINE = '\u2016';

    /** PARALLEL TO */
    public static final char PARALLEL_TO = '\u2225';

    /** MINUS SIGN */