system: 
You are an expert in composing functions. You are given a question and a set of possible functions.
Based on the question, you will need to make one or more function/tool calls to achieve the purpose.
If none of the function can be used, point it out. If the given question lacks the parameters required by the function,
also point it out. You should only return the function call in tools call sections.

If you decide to invoke any of the function(s), you MUST put it in the format of [func_name1(params_name1=params_value1, params_name2=params_value2...), func_name2(params)]

You SHOULD NOT include any other text in the response.

Here is a list of functions in JSON format that you can invoke.

[{'name': 'Payment_1_RequestPayment', 'description': 'Initiates a payment request from a specified contact or account. Note that the provided function is in Python 3 syntax.', 'parameters': {'type': 'dict', 'required': ['receiver', 'amount'], 'properties': {'receiver': {'type': 'string', 'description': 'The name or identifier of the contact or account to receive the payment request.'}, 'amount': {'type': 'float', 'description': 'The monetary value to be requested in USD.'}, 'private_visibility': {'type': 'boolean', 'description': 'Indicates if the transaction should be kept private. A private transaction will not be visible to others.', 'default': False}}}}, {'name': 'Payment_1_MakePayment', 'description': 'This function allows a user to send money to a friend or contact using a specified payment method. The transaction can be marked as private and the amount is specified in the local currency. Note that the provided function is in Python 3 syntax.', 'parameters': {'type': 'dict', 'required': ['payment_method', 'amount', 'receiver'], 'properties': {'payment_method': {'type': 'string', 'description': 'The source of money used for making the payment. This is the payment method that will be charged.', 'enum': ['app balance', 'debit card', 'credit card']}, 'amount': {'type': 'float', 'description': 'The amount of money to send, specified in the local currency (e.g., USD).'}, 'receiver': {'type': 'string', 'description': 'The name or account identifier of the contact to whom the money is being sent.'}, 'private_visibility': {'type': 'boolean', 'description': 'Whether the transaction is private (true) or public (false).', 'default': False}}}}, {'name': 'Trains_1_GetTrainTickets', 'description': 'Reserve tickets for a train journey by providing travel details and passenger information. Note that the provided function is in Python 3 syntax.', 'parameters': {'type': 'dict', 'required': ['_from', 'to', 'date_of_journey', 'journey_start_time', 'number_of_adults'], 'properties': {'_from': {'type': 'string', 'description': "Starting city for the train journey, in the format of 'City, State', such as 'San Francisco, CA'."}, 'to': {'type': 'string', 'description': "Ending city for the train journey, in the format of 'City, State', such as 'Los Angeles, CA'."}, 'date_of_journey': {'type': 'string', 'description': "Date of the train journey, in the format of 'MM/DD/YYYY'."}, 'journey_start_time': {'type': 'string', 'description': "Time of start of the train journey, in 24-hour format 'HH:MM'."}, 'number_of_adults': {'type': 'integer', 'description': 'Number of adults to reserve train tickets for.'}, 'trip_protection': {'type': 'boolean', 'description': 'Indicates whether to add trip protection to the reservation for an additional fee.', 'default': False}, 'class': {'type': 'string', 'description': 'Fare class for the train reservation.', 'enum': ['Value', 'Flexible', 'Business'], 'default': 'Value'}}}}, {'name': 'Trains_1_FindTrains', 'description': 'Finds available trains going to a specified destination on a given date. Note that the provided function is in Python 3 syntax.', 'parameters': {'type': 'dict', 'required': ['_from', 'to', 'date_of_journey'], 'properties': {'_from': {'type': 'string', 'description': "The name of the starting city for the train journey, in the format of 'City, State' (e.g., 'Boston, MA')."}, 'to': {'type': 'string', 'description': "The name of the destination city for the train journey, in the format of 'City, State' (e.g., 'New York, NY')."}, 'date_of_journey': {'type': 'string', 'description': "The date of the train journey, in the format 'MM/DD/YYYY' (e.g., '04/25/2023')."}, 'class': {'type': 'string', 'description': 'The fare class for the train reservation.', 'enum': ['Value', 'Flexible', 'Business'], 'default': 'Value'}, 'number_of_adults': {'type': 'integer', 'description': 'The number of adults to reserve train tickets for. Must be a positive integer.', 'default': 1}}}}, {'name': 'Weather_1_GetWeather', 'description': 'Retrieve the current or historical weather conditions for a specified city and date. Note that the provided function is in Python 3 syntax.', 'parameters': {'type': 'dict', 'required': ['city'], 'properties': {'city': {'type': 'string', 'description': "The name of the city for which to retrieve weather data, in the format 'City, State/Country' (e.g., 'Denver, CO' or 'Paris, FR')."}, 'date': {'type': 'string', 'description': "The date for which to retrieve the weather, in the format 'YYYY-MM-DD' (e.g., '2023-04-12'). If not provided, the current date's weather will be retrieved.", 'default': None}}}}]


user: send $50 to my friend Alex using my app balance? And make sure the transaction is private.

Available functions:
[{"name": "Payment_1_RequestPayment", "description": "Initiates a payment request from a specified contact or account.", "parameters": {"type": "dict", "required": ["receiver", "amount"], "properties": {"receiver": {"type": "string", "description": "The name or identifier of the contact or account to receive the payment request."}, "amount": {"type": "float", "description": "The monetary value to be requested in USD."}, "private_visibility": {"type": "boolean", "description": "Indicates if the transaction should be kept private. A private transaction will not be visible to others.", "default": false}}}}, {"name": "Payment_1_MakePayment", "description": "This function allows a user to send money to a friend or contact using a specified payment method. The transaction can be marked as private and the amount is specified in the local currency.", "parameters": {"type": "dict", "required": ["payment_method", "amount", "receiver"], "properties": {"payment_method": {"type": "string", "description": "The source of money used for making the payment. This is the payment method that will be charged.", "enum": ["app balance", "debit card", "credit card"]}, "amount": {"type": "float", "description": "The amount of money to send, specified in the local currency (e.g., USD)."}, "receiver": {"type": "string", "description": "The name or account identifier of the contact to whom the money is being sent."}, "private_visibility": {"type": "boolean", "description": "Whether the transaction is private (true) or public (false).", "default": false}}}}, {"name": "Trains_1_GetTrainTickets", "description": "Reserve tickets for a train journey by providing travel details and passenger information.", "parameters": {"type": "dict", "required": ["_from", "to", "date_of_journey", "journey_start_time", "number_of_adults"], "properties": {"_from": {"type": "string", "description": "Starting city for the train journey, in the format of 'City, State', such as 'San Francisco, CA'."}, "to": {"type": "string", "description": "Ending city for the train journey, in the format of 'City, State', such as 'Los Angeles, CA'."}, "date_of_journey": {"type": "string", "description": "Date of the train journey, in the format of 'MM/DD/YYYY'."}, "journey_start_time": {"type": "string", "description": "Time of start of the train journey, in 24-hour format 'HH:MM'."}, "number_of_adults": {"type": "integer", "description": "Number of adults to reserve train tickets for."}, "trip_protection": {"type": "boolean", "description": "Indicates whether to add trip protection to the reservation for an additional fee.", "default": false}, "class": {"type": "string", "description": "Fare class for the train reservation.", "enum": ["Value", "Flexible", "Business"], "default": "Value"}}}}, {"name": "Trains_1_FindTrains", "description": "Finds available trains going to a specified destination on a given date.", "parameters": {"type": "dict", "required": ["_from", "to", "date_of_journey"], "properties": {"_from": {"type": "string", "description": "The name of the starting city for the train journey, in the format of 'City, State' (e.g., 'Boston, MA')."}, "to": {"type": "string", "description": "The name of the destination city for the train journey, in the format of 'City, State' (e.g., 'New York, NY')."}, "date_of_journey": {"type": "string", "description": "The date of the train journey, in the format 'MM/DD/YYYY' (e.g., '04/25/2023')."}, "class": {"type": "string", "description": "The fare class for the train reservation.", "enum": ["Value", "Flexible", "Business"], "default": "Value"}, "number_of_adults": {"type": "integer", "description": "The number of adults to reserve train tickets for. Must be a positive integer.", "default": 1}}}}, {"name": "Weather_1_GetWeather", "description": "Retrieve the current or historical weather conditions for a specified city and date.", "parameters": {"type": "dict", "required": ["city"], "properties": {"city": {"type": "string", "description": "The name of the city for which to retrieve weather data, in the format 'City, State/Country' (e.g., 'Denver, CO' or 'Paris, FR')."}, "date": {"type": "string", "description": "The date for which to retrieve the weather, in the format 'YYYY-MM-DD' (e.g., '2023-04-12'). If not provided, the current date's weather will be retrieved.", "default": null}}}}]

Ground-truth function call:
[{"Payment_1_MakePayment": {"payment_method": ["app balance"], "amount": [50.0], "receiver": ["Alex"], "private_visibility": [true]}}]