akes a function from <code>A</code>s to iterators of <code>B</code>s, and an iterator of
  <code>A</code>s (<code>Iterator1</code>) and produces an iterator of <code>B</code>s (<code>Iterator2</code>)
  by applying the function to every element in <code>Iterator1</code> and  
appending the resulting iterators.</p>
 
  <p>That is, flatmap behaves as if it had been defined as follows:</p>
 
  <pre>  llists:flatmap(Fun, Iterator) -&gt;
      llists:append(llists:map(Fun, Iterator)).</pre>
 
  Example:
  <pre> 