@classmethod
def from_class(cls, target_class):
    """Create a FunctionDescriptor from a class.

        Args:
            cls: Current class which is required argument for classmethod.
            target_class: the python class used to create the function
                descriptor.

        Returns:
            The FunctionDescriptor instance created according to the class.
        """
    module_name = target_class.__module__
    class_name = target_class.__name__
    return cls(module_name, '__init__', class_name)
