@classmethod
def register_dimension(cls, name, base_unit):
    """
        Register a new dimension along with its base unit.

        Parameters
        ----------
        name : unicode
            The name of the dimension.
        base_unit : unicode
            The identifier of the dimension's base unit.

        Raises
        ------
        ValueError
            If the given dimension already exists.
        """
    if name in cls._defaults_per_dimension:
        raise ValueError('Dimension %s already exists' % name)
    cls._defaults_per_dimension[name] = base_unit
