code: def from_file(filename=None, io='auto', prefix_dir=None,
                    omit_facets=False):
          
          if isinstance(filename, Mesh):
              return filename
  
          if io == 'auto':
              if filename is None:
                  output( 'filename or io must be specified!' )
                  raise ValueError
              else:
                  io = MeshIO.any_from_filename(filename, prefix_dir=prefix_dir)
  
          output('reading mesh (%s)...' % (io.filename))
          tt = time.clock()
  
          trunk = io.get_filename_trunk()
          mesh = Mesh(trunk)
          mesh = io.read(mesh, omit_facets=omit_facets)
  
          output('...done in %.2f s' % (time.clock() - tt))
  
          mesh._set_shape_info()
  
          return mesh
docs: Read a mesh from a file.
  
          Parameters
          ----------
          filename : string or function or MeshIO instance or Mesh instance
              The name of file to read the mesh from. For convenience, a
              mesh creation function or a MeshIO instance or directly a Mesh
              instance can be passed in place of the file name.
          io : *MeshIO instance
              Passing *MeshIO instance has precedence over filename.
          prefix_dir : str
              If not None, the filename is relative to that directory.
          omit_facets : bool
              If True, do not read cells of lower dimension than the space
              dimension (faces and/or edges). Only some MeshIO subclasses
              support this!