class_docstr: beam with text, optical and textual score
docstr: creates genesis beam
docstr_tok: ["creates","genesis","beam"]
code: def __init__(self, lm, useNGrams):
      "creates genesis beam"
      self.optical = Optical(1.0, 0.0)
      self.textual = Textual("")
      self.lm = lm
      self.useNGrams = useNGrams
  
imports: from __future__ import division
  from __future__ import print_function
  import copy
label_desc: Use image node_id 1 to create a new Beam object  with example: obj = Beam(lm, useNGrams)