code: def get_fixed_block(self, keys=[], unbuffered=False):
          
          if unbuffered or not self._fixed_block:
              self._fixed_block = self._read_fixed_block()
          format = self.fixed_format
          # navigate down list of keys to get to wanted data
          for key in keys:
              format = format[key]
          return _decode(self._fixed_block, format)
docs: Get the decoded "fixed block" of settings and min/max data.
  
          A subset of the entire block can be selected by keys.