def _format_values(val, n, e_type):
  """Returns a feature formated value

  Args:
    val: `str`, "num1,num2,num3,...", value to format
    n: `int`, number of elememts within tuples
    e_type: `str`, the type of each elements within tuples

  Returns
    a list of tuples of e_type values
  """
  lst = [e_type(float(x)) for x in val.split(',')]
  return [lst[i:i+n] for i in range(0, len(lst), n)]