docs: def connect(self, key, func):
          """Connect a function to the given formatoption
  
          Parameters
          ----------
          key: str
              The rcParams key
          func: function
              The function that shall be called when the rcParams key changes.
              It must accept a single value that is the new value of the
              key."""
          key = self._get_depreceated(key)[0]
          if key is not None:
              self._connections[key].append(func)