code: def at_time_validate(ctx, param, value):
      
      # if they are doing commit_at, ensure the input is formatted correctly.
      if value is not None:
          if (re.search(r'([0-2]\d)(:[0-5]\d){1,2}', value) is None and
              re.search(r'\d{4}-[01]\d-[0-3]\d [0-2]\d:[0-5]\d(:[0-5]\d)?',
                        value) is None):
              raise click.BadParameter("A commit at time must be in one of the "
                                       "two formats: 'hh:mm[:ss]' or "
                                       "'yyyy-mm-dd hh:mm[:ss]' (seconds are "
                                       "optional).")
      ctx.obj['at_time'] = value
      return value
docs: Callback validating the at_time commit option.
  
      Purpose: Validates the `at time` option for the commit command. Only the
             | the following two formats are supported: 'hh:mm[:ss]' or
             | 'yyyy-mm-dd hh:mm[:ss]' (seconds are optional).
  
      @param ctx: The click context paramter, for receiving the object dictionary
                | being manipulated by other previous functions. Needed by any
                | function with the @click.pass_context decorator. Callback
                | functions such as this one receive this automatically.
      @type ctx: click.Context
      @param param: param is passed into a validation callback function by click.
                  | We do not use it.
      @type param: None
      @param value: The value that the user supplied for the at_time option.
      @type value: str
  
      @returns: The value that the user supplied, if it passed validation.
              | Otherwise, raises click.BadParameter
      @rtype: str