title: Checking if a substring exists in a counter dictionary of strings
body: <p>Suppose I have a <code>collections.Counter</code> object like this</p>
  <pre><code>c = Counter({('paragraphs', 'are', 'the'): 1,
           ('are', 'the', 'building'): 1,
           ('the', 'building', 'blocks'): 1,
           ('building', 'blocks', 'of'): 1,
           ('blocks', 'of', 'papers'): 1,
           ('many', 'students', 'define'): 1,
           ('students', 'define', 'paragraphs'): 1,
           ('define', 'paragraphs', 'in'): 1,
           ('paragraphs', 'in', 'terms'): 1,
           ('in', 'terms', 'of'): 1})
  </code></pre>
  <p>Now suppose I have a list</p>
  <pre><code>l = ['many', 'students']
  </code></pre>
  <p>I want to check if <code>l</code> is a subset of any of <code>c</code>'s items. Since <code>c</code> has <code>('many', 'students', 'define')</code> then by my definition <code>l</code> is a subset of <code>c</code>.</p>