 in the fit cycle and runs the fit loop. All callbacks are treated the same, but the following callback classes are distinguished for semantic convenience:</p>
<ul>
<li><code>agent</code> - the <a href="/mrl/agent.html#Agent"><code>Agent</code></a> being trained</li>
<li><code>template_cb</code> - the <a href="/mrl/template_callback.html#TemplateCallback"><code>TemplateCallback</code></a> to use for the fit cycle</li>
<li><code>samplers</code> - any <a href="/mrl/samplers.html#Sampler"><code>Sampler</code><