def anchor_inside_flags(self,flat_anchors,
                        valid_flags,
                        img_shape,
                        allowed_border=0):
        """Check whether the anchors are inside the border.

        Args:
            flat_anchors (torch.Tensor): Flatten anchors, shape (n, 4).
            valid_flags (torch.Tensor): An existing valid flags of anchors.
            img_shape (tuple(int)): Shape of current image.
            allowed_border (int, optional): The border to allow the valid anchor.
                Defaults to 0.

        Returns:
            torch.Tensor: Flags indicating whether the anchors are inside a \
                valid range.
        """
        img_h, img_w = img_shape[:2]
        if allowed_border >= 0:
            inside_flags = valid_flags & \
                (flat_anchors[:, 0] >= -allowed_border) & \
                (flat_anchors[:, 1] >= -allowed_border) & \
                (flat_anchors[:, 2] < img_w + allowed_border) & \
                (flat_anchors[:, 3] < img_h + allowed_border)
        else:
            inside_flags = valid_flags
        return inside_flags
Check whether the anchors are inside the border.

        Args:
            flat_anchors (torch.Tensor): Flatten anchors, shape (n, 4).
            valid_flags (torch.Tensor): An existing valid flags of anchors.
            img_shape (tuple(int)): Shape of current image.
            allowed_border (int, optional): The border to allow the valid anchor.
                Defaults to 0.

        Returns:
            torch.Tensor: Flags indicating whether the anchors are inside a                 valid range.
        
ppdet/modeling/heads/co_atss_head.py