Gets the Dimension with the ID dimensionId
from this list.


- dimensionId (Int64)
- ID of the dimension to get.

Dimension with the ID dimensionId or
null if the dimension is not found.

If the dimension is not found in this list, null is returned.
Note that when dealing with multi-select dimensions, it is possible
for the list to have multiple Dimension objects for the same
dimension. In this case, several share the same ID and this method does not
define which one is returned.