docstr: Returns HTML Body Section Header
code: def header(self):
      """Returns HTML Body Section Header"""
      return self._html_body_header
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import os
  import datetime
  from yattag import Doc, indent
label_desc: Use image node_id 7 for calling the CustomHtml obj's underlying member method code with example usage: obj.header() and returns: self