human
Complete this python program:
def header_property(wsgi_name):
assistant
#Here is the Python program you requested.

    """Creates a read-only header property.
    Args:
    wsgi_name (str): Case-sensitive name of the header as it would
    appear in the WSGI environ ``dict`` (i.e., \HTTP_*\)
    Returns:
    A property instance than can be assigned to a class variable.
    """
    def fget(self):
        try:
            return (self.env[wsgi_name] or None)
        except KeyError:
            return None
    return property(fget)