title: Angle between two non intersecting lines
body: <p>Consider there are two lines, <code>l1</code>, <code>l2</code> and they might be intersecting or non-intersecting. Is there any elegent way to find a angle between them? Thank you</p>
  
  <pre><code>import numpy as np
  from shapely import LineString
  
  l1 = [(0,0), (1,1)]
  l2 = [(0.5, 1), (0.5, 2)]
  
  ls1 = LineString(l1)
  ls2 = LineString(l2)
  
  angle = compute_angle(ls1, ls2)
  
  # This is I want to avoid because I have very big dataset and performance will degrade
  def compute_anlge(l1, l2):
     #Extend line1 and line2 in both direction util they intersect
  
     # Find intersection point
  
     # Create new lines with the intersection point
  
     # find angle and return
  </code></pre>