Question: One of the core files **classes/stock/StockAvailable.php** contains:

```
class StockAvailableCore extends ObjectModel
{
   public static function getQuantityAvailableByProduct($id_product = null, $id_product_attribute = null, $id_shop = null)
     {
       ...
     }
  ...
}

```

I want to call this **getQuantityAvailableByProduct()** method from my module.

So I tried to include this class (and it's father class and father's interface), extend it and call method like this:

```
require_once('../../src/Core/Foundation/Database/EntityInterface.php');
require_once('../../classes/ObjectModel.php');
require_once('../../classes/stock/StockAvailable.php');

$MyClass = new StockAvailableCore();

$MyClass->getStockAvailableIdByProductId($id);

```

And the error that I'm getting:

```
PHP Fatal error:  Uncaught Error: Class 'ObjectModel' not found in /home/mantas/Server/honey/classes/stock/StockAvailable.php:34

```

What am i missing? And is this the correct way to extend a class and call method?

Answer: 
In case someone else is ok with getting Python3.6 installed as a side effect (python3.7-distutils introduces it as pointed out by OP). This will install Python3.7 making it default and have the latest available `pip` using your python3.7 installation 

```
FROM ubuntu:18.04

# Upgrade installed packages
RUN apt-get update && apt-get upgrade -y && apt-get clean

# (...)

# Python package management and basic dependencies
RUN apt-get install -y curl python3.7 python3.7-dev python3.7-distutils

# Register the version in alternatives
RUN update-alternatives --install /usr/bin/python python /usr/bin/python3.7 1

# Set python 3 as the default python
RUN update-alternatives --set python /usr/bin/python3.7

# Upgrade pip to latest version
RUN curl -s https://bootstrap.pypa.io/get-pip.py -o get-pip.py && \
    python get-pip.py --force-reinstall && \
    rm get-pip.py

# (...)

```
If your only requirement is of python 3.7 and the version of the underlying os doesn't bothers you then you should go with the option of creating image from official python3.7 image. 
`FROM python:3.7`
And then install the required packages from requirements.txt