code: def before(func):
      
      class BeforeDecorator(LambdaDecorator):
          def before(self, event, context):
              return func(event, context)
  
      return BeforeDecorator
docs: Run a function before the handler is invoked, is passed the event & context
      and must return an event & context too.
  
      Usage::
  
          >>> # to create a reusable decorator
          >>> @before
          ... def print_request_id(event, context):
          ...     print(context.aws_request_id)
          ...     return event, context
          >>> @print_request_id
          ... def handler(event, context):
          ...     pass
          >>> class Context:
          ...     aws_request_id = 'ID!'
          >>> handler({}, Context())
          ID!
          >>> # or a one off
          >>> @before(lambda e, c: (e['body'], c))
          ... def handler(body, context):
          ...     return body
          >>> handler({'body': 'BOOODYY'}, object())
          'BOOODYY'