code: def _safe_get(mapping, key, default=None):
      
      try:
          return mapping.get(key, default)
      except AttributeError:
          return default
docs: Helper for accessing style values.
  
      It exists to avoid checking whether `mapping` is indeed a mapping before
      trying to get a key.  In the context of style dicts, this eliminates "is
      this a mapping" checks in two common situations: 1) a style argument is
      None, and 2) a style key's value (e.g., width) can be either a mapping or a
      plain value.