code: def get_relative_file_path(absolute_file_path):
      '''
      Example:
      absolute_file_path = "/home/xxx/Dev/openfisca/openfisca-france/openfisca_france/param/param.xml"
      result = "openfisca_france/param/param.xml"
      '''
      global country_package_dir_path
      assert country_package_dir_path is not None
      relative_file_path = absolute_file_path[len(country_package_dir_path):]
      if relative_file_path.startswith('/'):
          relative_file_path = relative_file_path[1:]
      return relative_file_patf get_relative_file_path(absolute_file_path):
      '''
      Example:
      absolute_file_path = "/home/xxx/Dev/openfisca/openfisca-france/openfisca_france/param/param.xml"
      result = "openfisca_france/param/param.xml"
      '''
      global country_package_dir_path
      assert country_package_dir_path is not None
      relative_file_path = absolute_file_path[len(country_package_dir_path):]
      if relative_file_path.startswith('/'):
          relative_file_path = relative_file_path[1:]
      return relative_file_path
docs: Example:
      absolute_file_path = "/home/xxx/Dev/openfisca/openfisca-france/openfisca_france/param/param.xml"
      result = "openfisca_france/param/param.xml"