docs: def or_(self, expression):
          ''' Adds the given expression to this instance's MongoDB ``$or``
              expression, starting a new one if one does not exst
  
              **Example**: ``(User.name == 'Jeff').or_(User.name == 'Jack')``
  
              .. note:: The prefered usageis via an operator: ``User.name == 'Jeff' | User.name == 'Jack'``
  
              '''
  
          if '$or' in self.obj:
              self.obj['$or'].append(expression.obj)
              return self
          self.obj = {
              '$or' : [self.obj, expression.obj]
          }
          return self