title: What do square brackets, "[]", mean in function/class documentation?
body: <p>I am having trouble figuring out the arguments to csv.dictreader and realized I have no clue what the square brackets signify.</p>
  
  <p>From the docmentation:</p>
  
  <pre><code>class csv.DictReader(csvfile[, fieldnames=None[, restkey=None[, restval=None[, dialect='excel'[, *args, **kwds]]]]])
  </code></pre>
  
  <p>I'd appreciate a summary of the arguments to the class instantiation.</p>
  
  <p>Thanks</p>