ct. Unavailable arguments are
represented by dummy objects that print as #<unavailable argument>. Objects
with dynamic-extent allocation by the current thread are represented by
substitutes to avoid references to them from leaking outside their legal
extent.</p>
<p>COUNT is the number of frames to backtrace, defaulting to
<em>BACKTRACE-FRAME-COUNT</em>.</p>
<p>START is the number of the frame the backtrace should start from.</p>
<p>FROM specifies the frame relative to which the frames are numbered. Possible