Converts input to a Shape.

  Args:
    x: Shape, str, or None.

  Returns:
    Shape or None.

  Raises:
    ValueError: If x cannot be converted to a Shape.

def convert_to_shape(x):
  """Converts input to a Shape.

  Args:
    x: Shape, str, or None.

  Returns:
    Shape or None.

  Raises:
    ValueError: If x cannot be converted to a Shape.
  """
  if x is None:
    return None
  if isinstance(x, Shape):
    return x
  if isinstance(x, str):
    x = _parse_string_to_list_of_pairs(x, seconds_to_int=True)
  return Shape(x)