code: def _read_meta_header(filename):
      
      fileIN = open(filename, 'r')
      line   = fileIN.readline()
  
      meta_dict = {}
      tag_flag = [False]*len(MHD_TAGS)
      while line:
          tags = str.split(line, '=')
          # print tags[0]
          for i in range(len(MHD_TAGS)):
              tag = MHD_TAGS[i]
              if (str.strip(tags[0]) == tag) and (not tag_flag[i]):
                  # print tags[1]
                  meta_dict[tag] = str.strip(tags[1])
                  tag_flag[i] = True
          line = fileIN.readline()
      #  comment
      fileIN.close()
      return meta_dict
docs: Return a dictionary of meta data from meta header file.
  
      Parameters
      ----------
      filename: str
          Path to a .mhd file
  
      Returns
      -------
      meta_dict: dict
          A dictionary with the .mhd header content.