There are numerous locations where a spontaneous mutation can occur, causing the disruption of one step in the melanin production process and resulting in an albino snake.
The albino and lavender albino genes are located on different alleles, therefore if bred together the offspring will still have one working melanin production gene at both alleles.
For example, Albino and Candy are located on the same allele, therefore breeding them together will produce an intermediate form of albinism known as a candino.
When breeding an Albino to a Lavender Albino each parent passes on one copy of their different albino gene and one normal gene for the opposing form of albino.
A lavender albino has 2 normal alleles for albino; an albino has 2 normal alleles for lavender albino.
Producing visual/ double homologous lavender albino albinos would likely be an waste of time/ resources, only resulting in an albino looking animal with a possible pattern influence from the lavender trait, as the albino gene's inability to produce blue pigment would likely dominate the lavender albino genes colors, and at the end of the day there are much more rewarding double het projects.