title: vim gd search for function name
body: <p>If I use gd on the function name for the following:</p>
  
  <pre><code>def function_name(parameter1, parameter2):
  ...
  ...
  </code></pre>
  
  <p>vim searches for "function_name(parameter1" but I want it to search only "function_name". 
  How can I do this?</p>