if the credential includes a password,
 this method would overwrite the password value.</div>
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<h4>isValid</h4>
<pre>default&nbsp;boolean&nbsp;isValid()</pre>
<div class="block">Determines whether the credential is valid. This would be called as part of
 the credential validation process to check the integrity of the credential,
 such as a signature check. This check would be self-contained,
 not requiring iden