code: def _strip_extra(elements):
      
      extra_indexes = []
      for i, element in enumerate(elements):
          if isinstance(element, list):
              cancelled = _strip_extra(element)
              if cancelled:
                  extra_indexes.append(i)
          elif isinstance(element, tuple) and element[0].value == "extra":
              extra_indexes.append(i)
      for i in reversed(extra_indexes):
          del elements[i]
          if i > 0 and elements[i - 1] == "and":
              # Remove the "and" before it.
              del elements[i - 1]
          elif elements:
              # This shouldn't ever happen, but is included for completeness.
              # If there is not an "and" before this element, try to remove the
              # operator after it.
              del elements[0]
      return (not elements)
docs: Remove the "extra == ..." operands from the list.
  
      This is not a comprehensive implementation, but relies on an important
      characteristic of metadata generation: The "extra == ..." operand is always
      associated with an "and" operator. This means that we can simply remove the
      operand and the "and" operator associated with it.