title: Comparing numpy datatypes to strings
body: <p>Many numpy functions take dtype arguments as either strings (like <code>"float64"</code>) or numpy datatypes (like <code>numpy.float64</code>) or even python datatypes (like <code>float</code>). </p>
  
  <p>I need to compare two datatypes and want to support this flexible interface. Is there a function under which all of these are forms are equivalent? I.e. I want the minimal function <code>f</code> such that </p>
  
  <p><code>f("float64") == f(numpy.float64) == f(float)</code></p>
  
  <p>What does numpy use internally?</p>