[Bug] navlayers initialization errors out

[pljoel]

Expected Behavior

A navigation layer object should be created when passing a name and a domain to mitreattack.navlayers.layer

Actual Behavior

The program errors out since in the init method uses self.__data (double underscore), but the rest of the code uses self._data (single underscore)

Steps to Reproduce the Problem

Follow example 2 of https://github.com/mitre-attack/mitreattack-python/tree/master/mitreattack/navlayers/core#creating-layers-programmatically

1. Init a navigation layer with a name and a domain

import mitreattack.navlayers as navlayers

layer_example = navlayers.Layer(name="example", domain="enterprise-attack")

Traceback (most recent call last):
  File "/Users/me/test/test.py", line 3, in test
    layer_example = navlayers.Layer(name="example", domain="enterprise-attack")
  File "/Users/me/.local/share/virtualenvs/test-XrAZKEUD/lib/python3.8/site-packages/mitreattack/navlayers/core/layer.py", line 19, in __init__
    self._build()
  File "/Users/me/.local/share/virtualenvs/test-XrAZKEUD/lib/python3.8/site-packages/mitreattack/navlayers/core/layer.py", line 82, in _build
    self.__layer = _LayerObj(self._data['name'],  self._data['domain'])
AttributeError: 'Layer' object has no attribute '_data'

Possible Solution

Change self.__data (double underscore) to self._data (single underscore).

[ArtificialErmine]

Thanks for bringing this to our attention!