affine

class BaseTransform(ABC):
    """Abstract base class for transforms.

    If the transform is invertible, implement via __neg__ method.
    """

    def append(self, other: 'BaseTransform'):
        """Append another transform to this one.

        This is used to try to concatenate transforms of the same type into
        a single step to speed things up (e.g. for CMTK transforms). If that's
        not possible or not useful, must raise a `NotImplementedError`.
        """
        raise NotImplementedError(f'Unable to append {type(other)} to {type(self)}')

    def check_if_possible(self, on_error: str = 'raise'):
        """Test if running the transform is possible."""
        return

    @abstractmethod
    def copy(self) -> 'BaseTransform':
        """Return copy."""
        pass

    @abstractmethod
    def xform(self, points: np.ndarray) -> np.ndarray:
        """Return copy.

        Must accept a (N, 3) numpy array as first input and return the
        transformed (N, 3) points as sole output.s
        """
        pass