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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def env_timestamp(name, required=False, default=empty):
 """Pulls an environment variable out of the environment and parses it to a ``datetime.datetime`` object. The environment variable is expected to be a timestamp in the form of a float. If the name is not present in the environment and no default is specified then a ``ValueError`` will be raised. :param name: The name of the environment variable be pulled :type name: str :param required: Whether the environment variable is required. If ``True`` and the variable is not present, a ``KeyError`` is raised. :type required: bool :param default: The value to return if the environment variable is not present. (Providing a default alongside setting ``required=True`` will raise a ``ValueError``) :type default: bool """

    if required and default is not empty:
        raise ValueError("Using `default` with `required=True` is invalid")

    value = get_env_value(name, required=required, default=empty)
    # change datetime.datetime to time, return time.struct_time type
    if default is not empty and value is empty:
        return default
    if value is empty:
        raise ValueError(
            "`env_timestamp` requires either a default value to be specified, "
            "or for the variable to be present in the environment"
        )

    timestamp = float(value)
    return datetime.datetime.fromtimestamp(timestamp)