d><td><p>Replace a header by name.</p></td></tr><tr id=Rule-HeaderOperationTemplate-Operation-REMOVE><td><code>REMOVE</code></td><td><p>Remove a header by name. Values are ignored.</p></td></tr><tr id=Rule-HeaderOperationTemplate-Operation-APPEND><td><code>APPEND</code></td><td><p>Append values to the existing header values.</p></td></tr></tbody></table></section><h2 id=TimeStamp>TimeStamp</h2><section><p>An instance field of type TimeStamp denotes that the expression for the field must evaluate to
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