class_docstr: Constrained delaunay triangulation
  
  Implementation based on [1]_.
  
  Parameters
  ----------
  pts : array
      Nx2 array of points.
  edges : array
      Nx2 array of edges (dtype=int).
  
  Notes
  -----
  * Delaunay legalization is not yet implemented. This produces a proper
    triangulation, but adding legalisation would produce fewer thin
    triangles.
  * The pts and edges arrays may be modified.
  
  References
  ----------
  .. [1] Domiter, V. and Žalik, B. Sweep‐line algorithm for constrained
     Delaunay triangulation
class_docstr_tok: ["Constrained","delaunay","triangulation","Implementation","based","on","[","1","]","_.","Parameters","--","--","--","--","--","pts",":","array","Nx2","array","of","points",".","edges",":","array","Nx2","array","of","edges","(","dtype=int",")",".","Notes","--","--","-","*","Delaunay","legalization","is","not","yet","implemented",".","This","produces","a","proper","triangulation",",","but","adding","legalisation","would","produce","fewer","thin","triangles",".","*","The","pts","and","edges","arrays","may","be","modified",".","References","--","--","--","--","--","..","[","1","]","Domiter",",","V.","and","\u017dalik",",","B.","Sweep\u2010line","algorithm","for","constrained","Delaunay","triangulation"]
docstr: Return True if *edge* is below the current front.
  
  One of the points in *edge* must be _on_ the front, at *front_index*.
docstr_tok: ["Return","True","if","*","edge","*","is","below","the","current","front",".","One","of","the","points","in","*","edge","*","must","be","_on_","the","front",",","at","*","front_index","*","."]
code: def _edge_below_front(self, edge, front_index):
      """Return True if *edge* is below the current front.
  
      One of the points in *edge* must be _on_ the front, at *front_index*.
      """
      f0 = self._front[front_index - 1]
      f1 = self._front[front_index + 1]
      return (
          self._orientation(edge, f0) > 0
          and self._orientation(edge, f1) < 0
      )
  
imports: from __future__ import division, print_function
  from itertools import permutations
  import numpy
  from collections import OrderedDict
label_desc: Use image node_id 13 for calling the Triangulation obj's underlying member method code with example usage: obj._edge_below_front(edge, front_index) and returns: unknown