code: def get(cls, resolvable_string, options_builder=None, interpreter=None):
      
      options_builder = options_builder or ResolverOptionsBuilder()
      for resolvable_impl in cls._REGISTRY:
        try:
          return resolvable_impl.from_string(resolvable_string,
                                             options_builder,
                                             interpreter=interpreter)
        except cls.InvalidRequirement:
          continue
      raise cls.InvalidRequirement('Unknown requirement type: %s' % resolvable_string)
docs: Get a :class:`Resolvable` from a string.
  
      :returns: A :class:`Resolvable` or ``None`` if no implementation was appropriate.