title: Is it possible to override "find" and "erase" methods of boost::bimaps::bimap.left? How to do it?
body: <p>I have following: </p>
  
  <pre><code>struct foo_and_number_helper {
    std::string foo;
    uint64_t number;
  };
  struct foo_and_number {};
  struct bar {};
  
  using my_bimap = boost::bimaps::bimap&lt;
    boost::bimaps::unordered_set_of&lt;boost::bimaps::tagged&lt;foo_and_number_helper, foo_and_number&gt;&gt;, 
    boost::bimaps::multiset_of&lt;boost::bimaps::tagged&lt;std::string, bar&gt;&gt;
  &gt;;
  
  my_bimap instance;
  </code></pre>
  
  <p>and I want to be able to call find and erase methods like this: <br>
  <code>instance.left.find("foo")</code> instead of <code>instance.left.find({"foo",1})</code> and<br>
  <code>instance.left.erase("foo")</code> instead of <code>instance.left.erase({"foo",1})</code>.</p>
  
  <p>I just want to use only the "foo" part of "foo_and_number_helper" instead of both parts for methods find and erase called from the left side. How to achieve that? I tried to read the bimap implementation, but it's still hard for me to do it.</p>
  
  <p>I already asked more broad question: <a href="https://stackoverflow.com/questions/50684467/is-c-bimap-possible-with-one-side-of-view-having-different-key-than-other-side">Is C++ bimap possible with one side of view having different key than other side of the view value? How to do that?</a>
  and from the comments I have to override <code>operator &lt;</code>, but I am not even sure about that and if it's enough.</p>