1 if the element is a member of the set
0 if the element is not a member of the set OR if the key does not exist
</pre><h2><a name="See also">See also</a></h2>
1 if the element is a member of the set
0 if the element is not a member of the set OR if the key does not exist
</pre><h2><a name="See also">See also</a></h2>