<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 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)