Availability:built-in
erase(+Reference)Erase a record or clause from the database. Reference is a
db-reference returned by recorda/3, recordz/3
or recorded/3, clause/3,
assert/2, asserta/2
or assertz/2.
Fail silently if the referenced object no longer exists. Notably, if
multiple threads attempt to erase the same clause one will succeed and
the others will fail.