docs: clarify Parameters for the add_files API

mkdocs/docs/api.md

@@ -1004,6 +1004,33 @@ To show only data files or delete files in the current snapshot, use `table.insp
 
 Expert Iceberg users may choose to commit existing parquet files to the Iceberg table as data files, without rewriting them.
 
+<!-- prettier-ignore-start -->
+
+!!! note "Name Mapping"
+Because `add_files` uses existing files without writing new parquet files that are aware of the Iceberg's schema, it requires the Iceberg's table to have a [Name Mapping](https://iceberg.apache.org/spec/?h=name+mapping#name-mapping-serialization) (The Name mapping maps the field names within the parquet files to the Iceberg field IDs). Hence, `add_files` requires that there are no field IDs in the parquet file's metadata, and creates a new Name Mapping based on the table's current schema if the table doesn't already have one.
+
+!!! note "Partitions"
+`add_files` only requires the client to read the existing parquet files' metadata footer to infer the partition value of each file. This implementation also supports adding files to Iceberg tables with partition transforms like `MonthTransform`, and `TruncateTransform` which preserve the order of the values after the transformation (Any Transform that has the `preserves_order` property set to True is supported). Please note that if the column statistics of the `PartitionField`'s source column are not present in the parquet metadata, the partition value is inferred as `None`.
+
+!!! warning "Maintenance Operations"
+Because `add_files` commits the existing parquet files to the Iceberg Table as any other data file, destructive maintenance operations like expiring snapshots will remove them.
+
+!!! warning "Check Duplicate Files"
+The `check_duplicate_files` parameter is `True` by default and will check the new files against the existing Iceberg table data files to prevent duplicates. This check can be expensive for large tables with many files. It is recommended to use the default configuration. The check can be turned off by setting `check_duplicate_files=False`, but this may result in duplicate files being added to the table, which can lead to data consistency issues and potential table corruption if the same data file is added multiple times.
+
+<!-- prettier-ignore-end -->
+
+### Usage
+
+| Parameter                 | Required? | Type           | Description                                                             |
+| ------------------------- | --------- | -------------- | ----------------------------------------------------------------------- |
+| `file_paths`            | ✔️      | List[str]      | The list of full file paths to be added as data files to the table      |
+| `snapshot_properties`   |           | Dict[str, str] | Properties to set for the new snapshot. Defaults to an empty dictionary |
+| `check_duplicate_files` |           | bool           | Whether to check for duplicate files. Defaults to `True`             |
+
+### Example
+
+Add files to Iceberg table:
 ```python
 # Given that these parquet files have schema consistent with the Iceberg table
 
@@ -1019,18 +1046,34 @@ tbl.add_files(file_paths=file_paths)
 # A new snapshot is committed to the table with manifests pointing to the existing parquet files
 ```
 
-<!-- prettier-ignore-start -->
+Add files to Iceberg table with custom snapshot properties:
+```python
+# Assume an existing Iceberg table object `tbl`
 
-!!! note "Name Mapping"
-    Because `add_files` uses existing files without writing new parquet files that are aware of the Iceberg's schema, it requires the Iceberg's table to have a [Name Mapping](https://iceberg.apache.org/spec/?h=name+mapping#name-mapping-serialization) (The Name mapping maps the field names within the parquet files to the Iceberg field IDs). Hence, `add_files` requires that there are no field IDs in the parquet file's metadata, and creates a new Name Mapping based on the table's current schema if the table doesn't already have one.
+file_paths = [
+    "s3a://warehouse/default/existing-1.parquet",
+    "s3a://warehouse/default/existing-2.parquet",
+]
 
-!!! note "Partitions"
-    `add_files` only requires the client to read the existing parquet files' metadata footer to infer the partition value of each file. This implementation also supports adding files to Iceberg tables with partition transforms like `MonthTransform`, and `TruncateTransform` which preserve the order of the values after the transformation (Any Transform that has the `preserves_order` property set to True is supported). Please note that if the column statistics of the `PartitionField`'s source column are not present in the parquet metadata, the partition value is inferred as `None`.
+# Custom snapshot properties
+snapshot_properties = {"abc": "def"}
 
-!!! warning "Maintenance Operations"
-    Because `add_files` commits the existing parquet files to the Iceberg Table as any other data file, destructive maintenance operations like expiring snapshots will remove them.
+# Enable duplicate file checking
+check_duplicate_files = True
 
-<!-- prettier-ignore-end -->
+# Add the Parquet files to the Iceberg table without rewriting
+tbl.add_files(
+    file_paths=file_paths,
+    snapshot_properties=snapshot_properties,
+    check_duplicate_files=check_duplicate_files
+)
+
+# NameMapping must have been set to enable reads
+assert tbl.name_mapping() is not None
+
+# Verify that the snapshot property was set correctly
+assert tbl.metadata.snapshots[-1].summary["abc"] == "def"
+```
 
 ## Schema evolution