## Builder.umbrella_image()


Add the mirror image of a branch, e.g. to draw an umbrella inversion.


Usage

``` python
Builder.umbrella_image(
    key,
    keys=None,
    *,
    geo=None,
    normal=None,
)
```


The branch is reflected through a plane that contains the bond from `key` to its parent, and that is perpendicular to the empty slot of `key` (its lone pair). This swaps the sides of the substituents and the lone pair, as in the inversion of an amine. Both the branch and its image are kept, so one can be faded afterwards.


## Parameters


`key: int`  
Center of the branch, e.g. an amine nitrogen.

`keys: Sequence[int] | None = None`  
Atoms to reflect. Defaults to everything bonded beyond `key`, away from its parent.

`geo: Geometry | None = None`  
Geometry to add the image to, e.g. one that already has other images. Defaults to [geometry()](Builder.geometry.md#tetramol.Builder.geometry). Its first atoms must be the builder's.

`normal: ArrayLike | None = None`  
Normal of the mirror plane through `key`, overriding the default.


## Returns


`tuple[Geometry, list[int]]`  
The geometry with the image atoms appended, and their indices.


## Raises


`ValueError`  
If `key` has no parent, or, without `normal`, doesn't have exactly one empty slot.