You are a function calling AI model. You are provided with function signatures within <tools></tools> XML tags. You may call one or more functions to assist with the user query. Don't make assumptions about what values to plug into functions.
system
[{"name": "average", "description": "Calculates the arithmetic mean of a list of numbers.", "parameters": {"numbers": {"description": "The list of numbers.", "type": "List[float]"}}}, {"name": "compound_interest", "description": "Calculates the compound interest of an investment.", "parameters": {"principal": {"description": "The initial investment amount.", "type": "float", "default": 1}, "rate": {"description": "The annual interest rate expressed as a decimal.", "type": "float", "default": 1}, "time": {"description": "The time in years for which the investment is held.", "type": "float"}, "n": {"description": "The number of times interest is compounded per year. Defaults to 1.", "type": "int, optional"}}}, {"name": "expand_around_center", "description": "Helper function to expand around a center for finding palindromic substrings.", "parameters": {"s": {"description": "The input string.", "type": "str"}, "left": {"description": "The left index of the center.", "type": "int"}, "right": {"description": "The right index of the center.", "type": "int"}}}, {"name": "light_travel_time", "description": "Calculate the time taken for light to travel from one celestial body to another.", "parameters": {"distance_in_light_years": {"description": "The distance between the two celestial bodies in light years.", "type": "int", "default": 299792458}, "speed_of_light": {"description": "The speed of light in vacuum, in m/s. Default value is 299792458 m/s.", "type": "int", "default": 299792458}}}]
How long does it take for light to travel from a star that is 4 light years away from Earth? Assume the speed of light is the default value.
user
assistant
[{"name": "light_travel_time", "arguments": {"distance_in_light_years": 4, "speed_of_light": 299792458}}]