The phrase "as is sometimes done" is correct and usable in written English.
It can be used to refer to a common practice or method that is occasionally employed in a particular context.
Example: "In academic writing, citations are often included at the end of a paper, as is sometimes done in research articles."
Alternatives: "as is occasionally practiced" or "as is often the case".
Yet, notwithstanding these measures, it would be wrong, as is sometimes done, to describe Alexander II as a liberal.
He mentioned shifting to uniformly slaughtering cattle at 24 months, not at 30 months or older as is sometimes done here now.
The king told a top White House aide, John O. Brennan, that the United States should implant an electronic chip in each detainee to track his movements, as is sometimes done with horses and falcons.
An early and general monophthongization of the diphthongs ai and au to ē and ō, respectively, also must be considered characteristic, although it should not be ascribed to Common Old Iranian as is sometimes done.
And it's delicious when added to the cooking liquid for basmati rice, as is sometimes done in Northern India; to my taste, one-half teaspoon or so per cup of dry rice is about right.
Likewise, all brackets modeled consisted from a single material phase, and no different materials were used for the tie-wings and base of the bracket, as is sometimes done for metallic brackets [37].
Many labels are noting that the garments have been mercerized -- not once, as was sometimes done in the past, but two or three times.
It involved securing an undertaking to buy on installments over many months an already published set of books; it could also be used to secure advance orders for an expensive work, probably in several volumes, that the publisher was planning to issue, as was sometimes done in the 18th century.
Clearing the pagefile is sometimes done as a security measure.
As hard as this is sometimes, don't let the idea that you're not good enough, clever enough, whatever enough, gnaw at your insides.
The Chicago accent does place emphasis on the short A sound (like in "cat" and "pat"), but it's not a harsh emphasis, nor does it extend to all vowel sounds as is sometimes jokingly done.
