title: in python how do I decompose a rotation matrix to a quaternion? (preferrably using the euclid library)
body: <p>I have started experimenting with the <a href="https://pypi.python.org/pypi/euclid" rel="nofollow">euclid module for python</a> .  I am now to the point where I want to take an arbitrary rotation matrix and decompose it into its quaternion form.  </p>
  
  <p>The formulas are available in a couple of places on the web (like <a href="http://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToQuaternion/" rel="nofollow">http://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToQuaternion/</a> ), but I was hoping there was an implementation somewhere inside the euclid library.</p>