code: def to_swc(self):
      
      from . import __version__
      swc = """# ORIGINAL_SOURCE CloudVolume {}
  # CREATURE 
  # REGION
  # FIELD/LAYER
  # TYPE
  # CONTRIBUTOR {}
  # REFERENCE
  # RAW 
  # EXTRAS 
  # SOMA_AREA
  # SHINKAGE_CORRECTION 
  # VERSION_NUMBER 
  # VERSION_DATE {}
  # SCALE 1.0 1.0 1.0
  
  """.format(
        __version__, 
        ", ".join([ str(_) for _ in self.vol.provenance.owners ]),
        datetime.datetime.utcnow().isoformat()
      )
  
      skel = self.clone()
  
      def parent(i):
        coords = np.where( skel.edges == i )
        edge = skel.edges[ coords[0][0] ]
        if edge[0] == i:
          return edge[1] + 1
        return edge[0] + 1
  
      for i in range(skel.vertices.shape[0]):
        line = "{n} {T} {x} {y} {z} {R} {P}".format(
            n=i+1,
            T=skel.vertex_types[i],
            x=skel.vertices[i][0],
            y=skel.vertices[i][1],
            z=skel.vertices[i][2],
            R=skel.radii[i],
            P=-1 if i == 0 else parent(i),
          )
  
        swc += line + '\n'
  
      return swc
docs: Prototype SWC file generator. 
  
      c.f. http://research.mssm.edu/cnic/swc.html