This is the description for a general position of a component.
It is recommended to name an instance of NXgeometry as "geometry"
to aid in the use of the definition in simulation codes such as McStas.
Also, in HDF, linked items must share the same name.
However, it might not be possible or practical in all situations.
shape/size information of component
translation of component
orientation of component
Optional description/label. Probably only present if we are an additional reference
point for components rather than the location of a real component
Position of the component along the beam path. The sample is at 0, components upstream
have negative component_index, components downstream have positive
component_index.