code: def setup(self, filters=()):
      
      # We filter the interpreter cache itself (and not just the interpreters we pull from it)
      # because setting up some python versions (e.g., 3<=python<3.3) crashes, and this gives us
      # an escape hatch.
      filters = filters if any(filters) else self.python_setup.interpreter_constraints
      setup_paths = self.python_setup.interpreter_search_paths
      logger.debug(
        'Initializing Python interpreter cache matching filters `{}` from paths `{}`'.format(
          ':'.join(filters), ':'.join(setup_paths)))
  
      interpreters = []
      def unsatisfied_filters():
        return [f for f in filters if len(list(self._matching(interpreters, [f]))) == 0]
  
      with OwnerPrintingInterProcessFileLock(path=os.path.join(self._cache_dir, '.file_lock')):
        interpreters.extend(self._setup_cached(filters=filters))
        if not interpreters or unsatisfied_filters():
          interpreters.extend(self._setup_paths(setup_paths, filters=filters))
  
      for filt in unsatisfied_filters():
        logger.debug('No valid interpreters found for {}!'.format(filt))
  
      matches = list(self._matching(interpreters, filters=filters))
      if len(matches) == 0:
        logger.debug('Found no valid interpreters!')
  
      logger.debug(
        'Initialized Python interpreter cache with {}'.format(', '.join([x.binary for x in matches])))
      return matches
docs: Sets up a cache of python interpreters.
  
      :param filters: A sequence of strings that constrain the interpreter compatibility for this
        cache, using the Requirement-style format, e.g. ``'CPython>=3', or just ['>=2.7','<3']``
        for requirements agnostic to interpreter class.
      :returns: A list of cached interpreters
      :rtype: list of :class:`pex.interpreter.PythonInterpreter`