docs: def read_header(filename):
      ''' returns a dictionary of values in the header of the given file '''
      header = {}
      in_header = False
      data = nl.universal_read(filename)
      lines = [x.strip() for x in data.split('\n')]
      for line in lines:
          if line=="*** Header Start ***":
              in_header=True
              continue
          if line=="*** Header End ***":
              return header
          fields = line.split(": ")
          if len(fields)==2:
              header[fields[0]] = fields[1]