docs: def count(cls, *criterion, **kwargs):
          """Returns a count of the instances meeting the specified
          filter criterion and kwargs.
  
          Examples:
  
              >>> User.count()
              500
  
              >>> User.count(country="India")
              300
  
              >>> User.count(User.age > 50, country="India")
              39
  
          """
          if criterion or kwargs:
              return cls.filter(
                  *criterion,
                  **kwargs).count()
          else:
              return cls.query.count()