def METHOD_NAME():
    """Return a list of all python shells by running ``which -a python3 python`` which
    will report full path to all python and python3 wrapper in current $PATH.
    Shown below is an expected output.
    .. code-block:: console
        $ which -a python3 python
        /Users/siddiq90/.local/share/virtualenvs/buildtest-KLOcDrW0/bin/python3
        /usr/local/bin/python3
        /usr/bin/python3
        /Users/siddiq90/.local/share/virtualenvs/buildtest-KLOcDrW0/bin/python
        /usr/bin/python
    Returns:
        list: A list of full path to python shells
    """
    python_shells = []
    if not shutil.which("which"):
        raise BuildTestError("Unable to find program 'which'. Please install 'which' ")
    cmd = BuildTestCommand("which -a python python3")
    cmd.execute()
    out = cmd.get_output()
    python_shells += [item.strip() for item in out]
    return python_shells