code: def _expand_sources(sources):
      '''
      Expands a user-provided specification of source files into a list of paths.
      '''
      if sources is None:
          return []
      if isinstance(sources, six.string_types):
          sources = [x.strip() for x in sources.split(',')]
      elif isinstance(sources, (float, six.integer_types)):
          sources = [six.text_type(sources)]
      return [path
              for source in sources
              for path in _glob(source)f _expand_sources(sources):
      '''
      Expands a user-provided specification of source files into a list of paths.
      '''
      if sources is None:
          return []
      if isinstance(sources, six.string_types):
          sources = [x.strip() for x in sources.split(',')]
      elif isinstance(sources, (float, six.integer_types)):
          sources = [six.text_type(sources)]
      return [path
              for source in sources
              for path in _glob(source)]
docs: Expands a user-provided specification of source files into a list of paths.