docs: def _blockread(self, fname):
          """
          Generator yields bsize lines from gdf file.
          Hidden method.
  
  
          Parameters
          ----------
          fname : str
              Name of gdf-file.
              
          
          Yields
          ------
          list
              file contents
              
          """
          with open(fname, 'rb') as f:
              while True:
                  a = []
                  for i in range(self.bsize):
                      line = f.readline()
                      if not line: break
                      a.append(line.split())
                  if a == []: raise StopIteration
                  yield a