code: def merge_pex_path(self, pex_path):
      
      if not pex_path:
        return
      self.pex_path = ':'.join(merge_split(self.pex_path, pex_path))
docs: Merges a new PEX_PATH definition into the existing one (if any).
      :param string pex_path: The PEX_PATH to merge.