docs: def _walk_src(self, targets, flags, pipeline):
          """Walk source and parse files."""
  
          for target in targets:
              for f in glob.iglob(target, flags=flags | glob.S):
                  if not os.path.isdir(f):
                      self.log('', 2)
                      self.log('> Processing: %s' % f, 1)
                      if pipeline:
                          try:
                              yield pipeline[0]._run_first(f)
                          except Exception as e:
                              err = self.get_error(e)
                              yield [filters.SourceText('', f, '', '', err)]
                      else:
                          try:
                              if self.default_encoding:
                                  encoding = filters.PYTHON_ENCODING_NAMES.get(
                                      self.default_encoding, self.default_encoding
                                  ).lower()
                                  encoding = codecs.lookup(encoding).name
                              else:
                                  encoding = self.default_encoding
                              yield [filters.SourceText('', f, encoding, 'file')]
                          except Exception as e:
                              err = self.get_error(e)
                              yield [filters.SourceText('', f, '', '', err)]