title: how do I sign data with pyme?
body: <p>I just installed <code>pyme</code> on my ubuntu system.  it was easy (thanks apt-get) and I can reproduce the example code (encrypting using a public key in my keyring).  now I would like to <em>sign</em> some data and I didn't manage to find any example code nor much documentation.</p>
  
  <p>this is what I've been doing:</p>
  
  <pre><code>&gt;&gt;&gt; plain = pyme.core.Data('this is just some sample text\n')
  &gt;&gt;&gt; cipher = pyme.core.Data()
  &gt;&gt;&gt; c = pyme.core.Context()
  &gt;&gt;&gt; c.set_armor(1)
  &gt;&gt;&gt; name='me@office.com'
  &gt;&gt;&gt; c.op_keylist_start(name, 0)
  &gt;&gt;&gt; r = c.op_keylist_next()
  &gt;&gt;&gt; c.op_sign(???)
  </code></pre>
  
  <p>I don't know what to give as parameters, the <code>op_sign</code> method tells me </p>
  
  <pre><code>&gt;&gt;&gt; help(c.op_sign)
  Help on function _funcwrap in module pyme.util:
  
  _funcwrap(*args, **kwargs)
      gpgme_op_sign(ctx, plain, sig, mode) -&gt; gpgme_error_t
  </code></pre>
  
  <p>but I do not know how to create such objects.</p>