def arg_from_keywords(node, arg):
    """Retrieves a keyword argument from the node's keywords.

    Args:
        node (ast.Call): a node that represents a function call. For more,
            see https://docs.python.org/3/library/ast.html#abstract-grammar.
        arg (str): the name of the argument.

    Returns:
        ast.keyword: the keyword argument if it is present. Otherwise, this returns ``None``.
    """
    for kw in node.keywords:
        if kw.arg == arg:
            return kw

    return None