title: Check if paramiko ssh connection is still alive
body: <p>Is there a way to check if a <code>paramiko</code> SSH connection is still alive?</p>
  
  <pre><code>In [1]: import paramiko
  
  In [2]: ssh = paramiko.SSHClient() 
  
  In [3]: ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
  
  In [4]: ssh.connect(hostname)
  </code></pre>
  
  <p>I want to mimic something like this (which doesn't currently exist)</p>
  
  <pre><code>In [5]: ssh.isalive()
  True
  </code></pre>