title: Import modules in package in ROS2
body: <p>I have created a package for ROS2 and I have added a Python repository I downloaded. The problem I am having is that in the original repository the modules from the own repo were imported directly while in mine I have to import them adding the ROS2 package name before the module, even though I am importing a module from the same repo, like:</p>
  
  <p><code>import planner_pkg.SimpleOneTrailerSystem as SimpleOneTrailerSystem</code></p>
  
  <p>while I would like:</p>
  
  <p><code>import SimpleOneTrailerSystem</code></p>
  
  <p>My ROS2 project structure is like:</p>
  
  <pre><code>ros2_ws
    src
      planner
        planner_pkg
          __init__.py
          SimpleOneTrailerSystem.py
          planner_node.py
          ...
        package.xml
        setup.py
  </code></pre>
  
  <p>package.xml</p>
  
  <pre><code>&lt;?xml version="1.0"?&gt;
  &lt;package format="2"&gt;
    &lt;name&gt;planner_pkg&lt;/name&gt;
    &lt;version&gt;0.0.1&lt;/version&gt;
    &lt;description&gt;This package contains algorithm for park planner&lt;/description&gt;
  
    &lt;maintainer email=""&gt;&lt;/maintainer&gt;
    &lt;license&gt;Apache License 2.0&lt;/license&gt;
  
    &lt;exec_depend&gt;rclpy&lt;/exec_depend&gt;
    &lt;exec_depend&gt;std_msgs&lt;/exec_depend&gt;
  
    &lt;!-- These test dependencies are optional
    Their purpose is to make sure that the code passes the linters --&gt;
    &lt;test_depend&gt;ament_copyright&lt;/test_depend&gt;
    &lt;test_depend&gt;ament_flake8&lt;/test_depend&gt;
    &lt;test_depend&gt;ament_pep257&lt;/test_depend&gt;
    &lt;test_depend&gt;python3-pytest&lt;/test_depend&gt;
  
    &lt;export&gt;
      &lt;build_type&gt;ament_python&lt;/build_type&gt;
    &lt;/export&gt;
  &lt;/package&gt;
  
  </code></pre>
  
  <p>setup.py:</p>
  
  <pre><code>from setuptools import setup
  
  package_name = 'planner_pkg'
  
  setup(
      name=package_name,
      version='0.0.0',
      packages=[package_name],
      data_files=[
          ('share/ament_index/resource_index/packages',
              ['resource/' + package_name]),
          ('share/' + package_name, ['package.xml']),
      ],
      install_requires=['setuptools'],
      zip_safe=True,
      author='',
      author_email='',
      maintainer='',
      maintainer_email='',
      keywords=['ROS'],
      classifiers=[
          'Intended Audience :: Developers',
          'License :: OSI Approved :: Apache Software License',
          'Programming Language :: Python',
          'Topic :: Software Development',
      ],
      description='Package containing examples of how to use the rclpy API.',
      license='Apache License, Version 2.0',
      tests_require=['pytest'],
      entry_points={
          'console_scripts': [
              'planner_node = planner_pkg.planner_node:main',
          ],
      },
  )
  
  </code></pre>