Supporting Arctic Backend Provider & Orderbook, Tick Data Example (#744)

* change weight_decay & batchsize

* del weight_decay

* big weight_decay

* mid weight_decay

* small layer

* 2 layer

* full layer

* no weight decay

* divide into two data source

* change parse field

* delete some debug

* add Toperator

* new format of arctic

* fix cache bug to arctic read

* fix connection problem

* add some operator

* final version for arcitc

* clear HZ cache

* remove not used function

* add topswrappers

* successfully import data and run first test

* A simpler version to support arctic

* Successfully run all high-freq expressions

* Black format and fix add docs

* Add docs for download and test data

* update scripts and docs

* Add docs

* fix bug

* Refine docs

* fix test bug

* fix CI error

* clean code

Co-authored-by: bxdd <bxddream@gmail.com>
Co-authored-by: wangwenxi.handsome <wangwenxi.handsome@gmail.com>
Co-authored-by: Young <afe.young@gmail.com>

examples/orderbook_data/README.md

@@ -0,0 +1,51 @@
+# Introduction
+
+This example tries to demonstrate how Qlib supports data without fixed shared frequency.
+
+For example,
+- Daily prices volume data are fixed-frequency data. The data comes in a fixed frequency (i.e. daily)
+- Orders are not fixed data and they may come at any time point
+
+To support such non-fixed-frequency, Qlib implements an Arctic-based backend.
+Here is an example to import and query data based on this backend.
+
+# Installation
+
+Please refer to [the installation docs](https://docs.mongodb.com/manual/installation/) of mongodb.
+Current version of script with default value tries to connect localhost **via default port without authentication**.
+
+Run following command to install necessary libraries
+```
+pip install pytest
+```
+
+# Importing example data
+
+
+1. (Optional) Please follow the first part of [this section](https://github.com/microsoft/qlib#data-preparation) to **get 1min data** of Qlib.
+2. Please follow following steps to download example data
+```bash
+cd examples/orderbook_data/
+wget http://fintech.msra.cn/stock_data/downloads/highfreq_orderboook_example_data.tar.bz2
+tar xf highfreq_orderboook_example_data.tar.bz2
+```
+
+3. Please import the example data to your mongo db
+```bash
+cd examples/orderbook_data/
+python create_dataset.py initialize_library  # Initialization Libraries
+python create_dataset.py import_data  # Initialization Libraries
+```
+
+# Query Examples
+
+After importing these data, you run `example.py` to create some high-frequency features.
+```bash
+cd examples/orderbook_data/
+pytest -s --disable-warnings example.py   # If you want run all examples
+pytest -s --disable-warnings example.py::TestClass::test_exp_10  # If you want to run specific example
+```
+
+
+# Known limitations
+Expression computing between different frequencies are not supported yet