new_contents: #!/usr/bin/env python
  # Copyright (c) 2015, Ecole Polytechnique Federale de Lausanne, Blue Brain Project
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  '''Function that checks if tree is planar'''
  
  
  import numpy as np
  from neurom.core.tree import val_iter, ipreorder
  
  def check_planar(tree, tol=0.1):
  
  	# extract the x,y,z coordinates of all the points in the tree
  	points = np.array([value[0:3] for value in val_iter(ipreorder(tree))])
  
  	points -= 
  
  	# calculate the covariance of the points
  	cov = np.cov(points.transpose())
  
  	# find the principal components
  	eigs, eigv = np.linalg.eig(cov)
  
  	# smallest component size
  
  	min_eigv = eigs[np.argmin(eigs)]
  
  	#sc = 2.*np.sqrt(6.251 * eigs) # 90%
  
  	return  min_eigv
  
  
  
  
  
subject: check for planar morphology within a tolerance