docs: def load(cls, path):
          """
          Loads an instance of the class from a file.
  
          Parameters
          ----------
          path : str
              Path to an HDF5 file.
  
          Examples
          --------
          This is an abstract data type, but let us say that ``Foo`` inherits
          from ``Saveable``. To construct an object of this class from a file, we
          do:
  
          >>> foo = Foo.load('foo.h5') #doctest: +SKIP
          """
          if path is None:
              return cls.load_from_dict({})
          else:
              d = io.load(path)
              return cls.load_from_dict(d)