You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: function.rs
    path of file: ./repos/arrow-datafusion/datafusion/sql/src/expr
    
    the code of the file until where you have to start completion: // Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional info
    
    pub(crate) fn check_unnest_args(args: &[Expr], schema: &DFSchema) -> Result<()> {
        // Currently only one argument is supported
        let arg = match args.len() {
            0 => {
                return plan_err!("unnest() requires at least one argument");
            }
            1 => &args[0],
            _ => {
                return not_impl_err!("unnest() does not support multiple arguments yet");
            }
        };
        // Check argument type, array types are supported
        match arg.get_type(schema)? {
            DataType::List(_)
            | DataType::LargeList(_)
            | DataType::FixedSizeList(_, _) => Ok(()),
            DataType::Struct(_) => {
                not_impl_err!("unnest() does not support struct yet")
            }
            DataType::Null => {
                not_impl_err!("unnest() does not support null yet")
            }
            _ => {
                plan_err!("unnest() can only be applied to array, struct and null")
            }
        }
    }