title: Why aren't all bigrams created in gensim's `Phrases` tool?
body: <p>I have created a bigram model using gensim and the try to get the bigram sentences but it's not picking all bigram sentences why?</p>
  <pre class="lang-py prettyprint-override"><code>from gensim.models.phrases import Phrases, Phraser
  phrases = Phrases(sentences, min_count=1, threshold=1)
  bigram_model = Phraser(phrases)
  sent = [u'the', u'mayor', u'of', u'new', u'york', u'was', u'there']
  print(bigram_model[sent])
  [u'the', u'mayor', u'of', u'new_york', u'was', u'there']
  </code></pre>
  <p>Can anyone explain how to get all bigrams.</p>
  <h1>Why only 'new_york' not 'the_mayor' and others?</h1>