fix linting issues identified by ruff

Author: elong0527

src/rtflite/encoding/strategies.py

@@ -1025,7 +1025,8 @@ def encode(self, document: "RTFDocument") -> str:
                 page_elements.extend(header_elements)
 
             # Add page_by spanning table row after headers if specified
-            # Only if pageby_row is not 'column' (which keeps the column instead of spanning row)
+            # Only if pageby_row is not 'column'
+            # (which keeps the column instead of spanning row)
             # OR if not new_page (legacy behavior implies spanning rows)
             if page_info.get("pageby_header_info") and (
                 not document.rtf_body.new_page

src/rtflite/services/document_service.py

@@ -329,7 +329,8 @@ def apply_pagination_borders(
             and document.rtf_body.border_first
         ):
             # Apply border_first to first data row, respecting per-column settings
-            # Only use border_top if it has non-empty values; empty means use border_first
+            # Only use border_top if it has non-empty values;
+            # empty means use border_first
             if isinstance(document.rtf_body.border_first, list):
                 border_first_row = document.rtf_body.border_first[0]
                 has_border_top = (
@@ -345,7 +346,8 @@ def apply_pagination_borders(
                     else:
                         border_style = border_first_row[0]
 
-                    # Only override with border_top if it has a non-empty value for this column
+                    # Only override with border_top if it has a non-empty value
+                    # for this column
                     if (
                         has_border_top
                         and col_idx < len(document.rtf_body.border_top[0])
@@ -370,8 +372,10 @@ def apply_pagination_borders(
 
         # Apply page-level borders for non-first/last pages
         if not page_info["is_first_page"] and document.rtf_body.border_first:
-            # Apply border_first to first row of non-first pages, respecting per-column settings
-            # Only use border_top if it has non-empty values; empty means use border_first
+            # Apply border_first to first row of non-first pages,
+            # respecting per-column settings
+            # Only use border_top if it has non-empty values;
+            # empty means use border_first
             if isinstance(document.rtf_body.border_first, list):
                 border_first_row = document.rtf_body.border_first[0]
                 has_border_top = (
@@ -387,7 +391,8 @@ def apply_pagination_borders(
                     else:
                         border_style = border_first_row[0]
 
-                    # Only override with border_top if it has a non-empty value for this column
+                    # Only override with border_top if it has a non-empty value
+                    # for this column
                     if (
                         has_border_top
                         and col_idx < len(document.rtf_body.border_top[0])

src/rtflite/services/encoding_service.py

@@ -368,11 +368,13 @@ def prepare_dataframe_for_body_encoding(self, df, rtf_attrs):
 
         # Remove page_by columns from table display
         # page_by columns are shown as spanning rows, not as table columns
-        # The new_page flag only controls whether to force page breaks at group boundaries
+        # The new_page flag only controls whether to force page breaks
+        # at group boundaries
         if rtf_attrs.page_by is not None:
             # Restore previous behavior:
             # - If new_page=True: Respect pageby_row (default 'column' -> keep column)
-            # - If new_page=False: Always remove columns (legacy behavior implies spanning rows)
+            # - If new_page=False: Always remove columns (legacy behavior
+            #   implies spanning rows)
             if rtf_attrs.new_page:
                 pageby_row = getattr(rtf_attrs, "pageby_row", "column")
                 if pageby_row != "column":
@@ -389,12 +391,12 @@ def prepare_dataframe_for_body_encoding(self, df, rtf_attrs):
 
             # Handle attribute slicing for removed columns
             # We need to slice list-based attributes to match the new column structure
-            from copy import deepcopy
             from ..attributes import BroadcastValue
 
             # Create a copy of attributes to modify
             # We use deepcopy to ensure nested lists are copied
-            # model_copy(deep=True) is not sufficient for nested lists in Pydantic v2 sometimes
+            # model_copy(deep=True) is not sufficient for nested lists in
+            # Pydantic v2 sometimes
             processed_attrs = rtf_attrs.model_copy(deep=True)
 
             # Get indices of removed columns in the original dataframe