docs: def _readbin(fid, fmt='i', nwords=1, file64=False, unpack=True):
      """Read n words of 4 or 8 bytes with fmt format.
  
      fmt: 'i' or 'f' or 'b' (integer or float or bytes)
      4 or 8 bytes: depends on header
  
      Return an array of elements if more than one element.
  
      Default: read 1 word formatted as an integer.
      """
      if fmt in 'if':
          fmt += '8' if file64 else '4'
      elts = np.fromfile(fid, fmt, nwords)
      if unpack and len(elts) == 1:
          elts = elts[0]
      return elts