refactor: resolve identifier package names in nodes.py (#1385)

* fix: resolve identifier package names in nodes.py

* fix format

* revert table.num_rows change

Author: sycai

bigframes/core/nodes.py

@@ -800,7 +800,7 @@ class ReadLocalNode(LeafNode):
     # Mapping of local ids to bfet id.
     scan_list: ScanList
     # Offsets are generated only if this is non-null
-    offsets_col: Optional[bigframes.core.identifiers.ColumnId] = None
+    offsets_col: Optional[identifiers.ColumnId] = None
     session: typing.Optional[bigframes.session.Session] = None
 
     @property
@@ -1039,7 +1039,7 @@ class CachedTableNode(ReadTableNode):
 # Unary nodes
 @dataclasses.dataclass(frozen=True, eq=False)
 class PromoteOffsetsNode(UnaryNode, AdditiveNode):
-    col_id: bigframes.core.identifiers.ColumnId
+    col_id: identifiers.ColumnId
 
     @property
     def non_local(self) -> bool:
@@ -1317,9 +1317,7 @@ def remap_refs(
 class ProjectionNode(UnaryNode, AdditiveNode):
     """Assigns new variables (without modifying existing ones)"""
 
-    assignments: typing.Tuple[
-        typing.Tuple[ex.Expression, bigframes.core.identifiers.ColumnId], ...
-    ]
+    assignments: typing.Tuple[typing.Tuple[ex.Expression, identifiers.ColumnId], ...]
 
     def _validate(self):
         input_types = self.child._dtype_lookup
@@ -1445,9 +1443,7 @@ def remap_refs(
 
 @dataclasses.dataclass(frozen=True, eq=False)
 class AggregateNode(UnaryNode):
-    aggregations: typing.Tuple[
-        typing.Tuple[ex.Aggregation, bigframes.core.identifiers.ColumnId], ...
-    ]
+    aggregations: typing.Tuple[typing.Tuple[ex.Aggregation, identifiers.ColumnId], ...]
     by_column_ids: typing.Tuple[ex.DerefOp, ...] = tuple([])
     order_by: Tuple[OrderingExpression, ...] = ()
     dropna: bool = True
@@ -1539,7 +1535,7 @@ def remap_refs(
 class WindowOpNode(UnaryNode, AdditiveNode):
     expression: ex.Aggregation
     window_spec: window.WindowSpec
-    output_name: bigframes.core.identifiers.ColumnId
+    output_name: identifiers.ColumnId
     never_skip_nulls: bool = False
     skip_reproject_unsafe: bool = False
 
@@ -1682,7 +1678,7 @@ def remap_refs(
 class ExplodeNode(UnaryNode):
     column_ids: typing.Tuple[ex.DerefOp, ...]
     # Offsets are generated only if this is non-null
-    offsets_col: Optional[bigframes.core.identifiers.ColumnId] = None
+    offsets_col: Optional[identifiers.ColumnId] = None
 
     @property
     def row_preserving(self) -> bool: