LISP problem

[stepha301]

here is a piece of code. can anyone explain me what this is doing ?
thx
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(defun find-all (item sequence &rest keyword-args &key (test #'eql) test-not &allow-other-keys)
(if test-not
(apply #'remove item sequence
:test-not (complement test-not) keyword-args)
(apply #'remove item sequence
:test (complement test) keyword-args)))