Add docstrings for remaining high-priority methods

- Add docstrings to S3FileSystem.checksum(), sign(), cp_file() methods
- Add docstring to S3Object.to_dict() method
- Add docstrings to AthenaPandasResultSet.is_unload and dtypes properties
- Add docstring to BaseCursor.get_default_converter() static method
- Fix indentation issues in all added docstrings

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: laughingman7743

pyathena/common.py

@@ -183,6 +183,15 @@ def __init__(
 
     @staticmethod
     def get_default_converter(unload: bool = False) -> Union[DefaultTypeConverter, Any]:
+        """Get the default type converter for this cursor class.
+
+        Args:
+            unload: Whether the converter is for UNLOAD operations. Some cursor
+                   types may return different converters for UNLOAD operations.
+
+        Returns:
+            The default type converter instance for this cursor type.
+        """
         return DefaultTypeConverter()
 
     @property

pyathena/filesystem/s3.py

@@ -738,6 +738,28 @@ def touch(self, path: str, truncate: bool = True, **kwargs) -> Dict[str, Any]:
     def cp_file(
         self, path1: str, path2: str, recursive=False, maxdepth=None, on_error=None, **kwargs
     ):
+        """Copy an S3 object to another S3 location.
+
+        Performs server-side copy of S3 objects, which is more efficient than
+        downloading and re-uploading. Automatically chooses between simple copy
+        and multipart copy based on object size.
+
+        Args:
+            path1: Source S3 path (s3://bucket/key).
+            path2: Destination S3 path (s3://bucket/key).
+            recursive: Unused parameter for fsspec compatibility.
+            maxdepth: Unused parameter for fsspec compatibility.
+            on_error: Unused parameter for fsspec compatibility.
+            **kwargs: Additional S3 copy parameters (e.g., metadata, storage class).
+
+        Raises:
+            ValueError: If trying to copy to a versioned file or copy buckets.
+
+        Note:
+            Uses multipart copy for objects larger than the maximum part size
+            to optimize performance for large files. The copy operation is
+            performed entirely on the S3 service without data transfer.
+        """
         # TODO: Delete the value that seems to be a typo, onerror=false.
         # https://github.com/fsspec/filesystem_spec/commit/346a589fef9308550ffa3d0d510f2db67281bb05
         # https://github.com/fsspec/filesystem_spec/blob/2024.10.0/fsspec/spec.py#L1185
@@ -972,13 +994,59 @@ def get_file(self, rpath: str, lpath: str, callback=_DEFAULT_CALLBACK, outfile=N
                 callback.relative_update(len(data))
 
     def checksum(self, path: str, **kwargs):
+        """Get checksum for S3 object or directory.
+
+        Computes a checksum for the specified S3 path. For individual objects,
+        returns the ETag converted to an integer. For directories, returns a
+        checksum based on the directory's tokenized representation.
+
+        Args:
+            path: S3 path (s3://bucket/key) to get checksum for.
+            **kwargs: Additional arguments including:
+                refresh: If True, refresh cached info before computing checksum.
+
+        Returns:
+            Integer checksum value derived from S3 ETag or directory token.
+
+        Note:
+            For multipart uploads, ETag format is different and only the first
+            part before the dash is used for checksum calculation.
+        """
         refresh = kwargs.pop("refresh", False)
         info = self.info(path, refresh=refresh)
         if info.get("type") != S3ObjectType.S3_OBJECT_TYPE_DIRECTORY:
             return int(info.get("etag").strip('"').split("-")[0], 16)
         return int(tokenize(info), 16)
 
     def sign(self, path: str, expiration: int = 3600, **kwargs):
+        """Generate a presigned URL for S3 object access.
+
+        Creates a presigned URL that allows temporary access to an S3 object
+        without requiring AWS credentials. Useful for sharing files or providing
+        time-limited access to resources.
+
+        Args:
+            path: S3 path (s3://bucket/key) to generate URL for.
+            expiration: URL expiration time in seconds. Defaults to 3600 (1 hour).
+            **kwargs: Additional parameters including:
+                client_method: S3 operation ('get_object', 'put_object', etc.).
+                             Defaults to 'get_object'.
+                Additional parameters passed to the S3 operation.
+
+        Returns:
+            Presigned URL string that provides temporary access to the S3 object.
+
+        Example:
+            >>> fs = S3FileSystem()
+            >>> url = fs.sign("s3://my-bucket/file.txt", expiration=7200)
+            >>> # URL valid for 2 hours
+            >>>
+            >>> # Generate upload URL
+            >>> upload_url = fs.sign(
+            ...     "s3://my-bucket/upload.txt",
+            ...     client_method="put_object"
+            ... )
+        """
         bucket, key, version_id = self.parse_path(path)
         client_method = kwargs.pop("client_method", "get_object")
         params = {"Bucket": bucket, "Key": key}

pyathena/filesystem/s3_object.py

@@ -163,6 +163,11 @@ def __str__(self):
         return str(self.__dict__)
 
     def to_dict(self) -> Dict[str, Any]:
+        """Convert S3Object to dictionary representation.
+
+        Returns:
+            Deep copy of the object's attributes as a dictionary.
+        """
         return copy.deepcopy(self.__dict__)
 
     def to_api_repr(self) -> Dict[str, Any]:

pyathena/pandas/result_set.py

@@ -349,10 +349,22 @@ def __s3_file_system(self):
 
     @property
     def is_unload(self):
+        """Check if this result set comes from an UNLOAD operation.
+
+        Returns:
+            True if this result set is from an UNLOAD query and unload mode
+            is enabled, False otherwise.
+        """
         return self._unload and self.query and self.query.strip().upper().startswith("UNLOAD")
 
     @property
     def dtypes(self) -> Dict[str, Type[Any]]:
+        """Get pandas-compatible data types for result columns.
+
+        Returns:
+            Dictionary mapping column names to their corresponding Python types
+            based on the converter's type mapping.
+        """
         description = self.description if self.description else []
         return {
             d[0]: self._converter.types[d[1]] for d in description if d[1] in self._converter.types