code: def angle(array_of_xyzs):
      
      ab = array_of_xyzs[0] - array_of_xyzs[1]
      cb = array_of_xyzs[2] - array_of_xyzs[1]
      return np.arccos((np.dot(ab,cb)) / (np.sqrt(ab[0]**2 + ab[1]**2  \
          + ab[2]**2) * np.sqrt(cb[0]**2 + cb[1]**2 + cb[2]**2)))
docs: Calculates angle between three coordinate points (I could not find a package
      that does this but if one exists that would probably be better). Used for Angle constraints.