code: def remove(self, email):
          
          if email in self._collaborators:
              if self._collaborators[email] == ShareRequestValue.Add:
                  del self._collaborators[email]
              else:
                  self._collaborators[email] = ShareRequestValue.Remove
          self._dirty = True
docs: Remove a Collaborator.
  
          Args:
              str : Collaborator email address.