code: def transcript_to_gpd_line(tx,transcript_name=None,gene_name=None,direction=None):
      
      tname = tx._options.name
      if transcript_name: tname = transcript_name
      gname = tx._options.gene_name
      if gene_name: gname = gene_name
      dir = tx._options.direction
      if direction: dir = direction
      # check for if we just have a single name
      if not tname: tname = str(uuid.uuid4())
      if not gname:
          gname = tname
      out = ''
      out += gname + "\t"
      out += tname + "\t"
      out += tx.exons[0].chr + "\t"
      out += dir + "\t"
      out += str(tx.exons[0].start-1) + "\t"
      out += str(tx.exons[-1].end) + "\t"
      out += str(tx.exons[0].start-1) + "\t"
      out += str(tx.exons[-1].end) + "\t"
      out += str(len(tx.exons)) + "\t"
      out += str(','.join([str(x.start-1) for x in tx.exons]))+','+"\t"
      out += str(','.join([str(x.end) for x in tx.exons]))+','
      return out
docs: Get the genpred format string representation of the mapping
  
      :param transcript_name:
      :param gene_name:
      :param strand:
      :type transcript_name: string
      :type gene_name: string
      :type strand: string
      :return: GPD line
      :rtype: string