title: Cpp - Check if key exist in boost bimap
body: <p>I have a bimap. I want to check if key exists in my bimap. How can i do that. Here is my bimap: </p>
  
  <pre><code>namespace bimap
              {
  
                  struct Name{};
                  struct ID{};
  
                  typedef
                      boost::bimaps::bimap&lt;
                          boost::bimaps::set_of&lt; 
                              boost::bimaps::tagged&lt;
                                  unsigned short
                                  , ID
                              &gt;
                          &gt;,
  
                          boost::bimaps::set_of&lt;
                                  boost::bimaps::tagged&lt;
                                  std::string
                                  , Name
                              &gt;
                          &gt;
                      &gt;
                      name_index_bimap;
              }
  </code></pre>
  
  <p>I want to check if 'Name' is exists.</p>