def downsampling(data, interval):
  """Downsampling data with interval.
  Args:
    data: a list.
    interval: a int type number.

  Returns:
    a new list with downsampling
  """
  length = len(data)
  assert interval > 0
  ret = []
  for idx in range(0, length, interval):
    ret.append(data[idx])
  return ret