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: builtins.rs
    path of file: ./repos/greptimedb/src/script/src/python/rspython
    
    the code of the file until where you have to start completion: // Copyright 2023 Greptime Team
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//!  Builtin module contains GreptimeDB builtin udf/udaf

#[cfg(test)]
mod test;

use std::sync::Arc;

use datafusion_common::{DataFusionError, ScalarValue};
use datafusion_expr::ColumnarValue as DFColValue;
use datafusion_physical_expr::AggregateExpr;
use datatypes::arrow::array::ArrayRef;
use datatypes::arrow::compute;
use datatypes::arrow::datatypes::{DataType as ArrowDataType, Field};
use datatypes::vectors::Helper as HelperVec;
use rustpython_vm::builtins::{PyBaseExceptionRef, PyBool, PyFloat, PyInt, PyList, PyStr};
use rustpython_vm::{pymodule, AsObject, PyObjectRef, PyPayload, PyResult, VirtualMachine};

use crate::python::ffi_types::PyVector;
use crate::python::
    
    fn datetime(input: &PyStr, vm: &VirtualMachine) -> PyResult<i64> {
        let mut parsed = Vec::new();
        let mut prev = 0;
        #[derive(Debug)]
        enum State {
            Num(i64),
            Separator(String),
        }
        let mut state = State::Num(Default::default());
        let input = input.as_str();
        for (idx, ch) in input.chars().enumerate() {
            match (ch.is_ascii_digit(), &state) {
                (true, State::Separator(_)) => {
                    let res = &input[prev..idx];
                    let res = State::Separator(res.to_string());
                    parsed.push(res);
                    prev = idx;
                    state = State::Num(Default::default());
                }
                (false, State::Num(_)) => {
                    let res = str::parse(&input[prev..idx]).map_err(|err| {
                        vm.new_runtime_error(format!("Fail to parse num: {err:#?}"))
                    })?;
                    let res = State::Num(res);
                    parsed.push(res);
                    prev = idx;
                    state = State::Separator(Default::default());
                }
                _ => continue,
            };
        }
        let last = match state {
            State::Num(_) => {
                let res = str::parse(&input[prev..])
                    .map_err(|err| vm.new_runtime_error(format!("Fail to parse num: {err:#?}")))?;
                State::Num(res)
            }
            State::Separator(_) => {
                let res = &input[prev..];
                State::Separator(res.to_string())
            }
        };
        parsed.push(last);
        let mut cur_idx = 0;
        let mut tot_time = 0;
        fn factor(unit: &str, vm: &VirtualMachine) -> PyResult<i64> {
            let ret = match unit {
                "d" => 24 * 60 * 60,
                "h" => 60 * 60,
                "m" => 60,
                "s" => 1,
                _ => return Err(vm.new_type_error(format!("Unknown time unit: {unit}"))),
            };
            Ok(ret)
        }
        while cur_idx < parsed.len() {
            match &parsed[cur_idx] {
                State::Num(v) => {
                    if cur_idx + 1 > parsed.len() {
                        return Err(vm.new_runtime_error(
                            "Expect a separator after number, found nothing!".to_string(),
                        ));
                    }
                    let nxt = &parsed[cur_idx + 1];
                    if let State::Separator(sep) = nxt {
                        tot_time += v * factor(sep, vm)?;
                    } else {
                        return Err(vm.new_runtime_error(format!(
                            "Expect a separator after number, found `{nxt:#?}`"
                        )));
                    }
                    cur_idx += 2;
                }
                State::Separator(sep) => {
                    return Err(vm.new_runtime_error(format!("Expect a number, found `{sep}`")))
                }
            }
        }
        Ok(tot_time)
    }