import lxml
full_xml_tree = lxml.etree.parse('myfile.xml')

AttributeError: module 'lxml' has no attribute 'etree'

import lxml.etree
full_xml_tree = lxml.etree.parse('myfile.xml')

import xml.etree.ElementTree as ET
tree = ET.parse('myfile.xml')

test_pkg/__init__.py
test_pkg/shown_module.py
test_pkg/hidden_module.py

from . import shown_module

>>> import test_pkg
>>> test_pkg.shown_module
<module 'test_pkg.shown_module' from '.../test_pkg/shown_module.py'>

>>> test_pkg.hidden_module
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: module 'test_pkg' has no attribute 'hidden_module'

>>> import test_pkg.hidden_module
>>> test_pkg.hidden_module
<module 'test_pkg.hidden_module' from '.../test_pkg/hidden_module.py'>