parameters: (self, iterable, key=None)
docstring: List unique elements, preserving order.
          Remember all elements ever seen.
  
          _unique_everseen('AAAABBBCCDAABBB') --> A B C D
  
          _unique_everseen('ABBCcAD', str.lower) --> A B C D
docstring_summary: List unique elements, preserving order.
          Remember all elements ever seen.
docstring_tokens: List unique elements preserving order . Remember all elements ever seen .
function: def _unique_everseen(self, iterable, key=None):
          """
          List unique elements, preserving order.
          Remember all elements ever seen.
  
          _unique_everseen('AAAABBBCCDAABBB') --> A B C D
  
          _unique_everseen('ABBCcAD', str.lower) --> A B C D
          """
          seen = set()
          seen_add = seen.add
          if key is None:
              for element in filterfalse(seen.__contains__, iterable):
                  seen_add(element)
                  yield element
          else:
              for element in iterable:
                  k = key(element)
                  if k not in seen:
                      seen_add(k)
                      yield element
function_tokens: def _unique_everseen ( self , iterable , key = None ) : seen = set ( ) seen_add = seen . add if key is None : for element in filterfalse ( seen . __contains__ , iterable ) : seen_add ( element ) yield element else : for element in iterable : k = key ( element ) if k not in seen : seen_add ( k ) yield element