Removed return value and make target_file positional

We should convince the users to download the file first and then use it
instead of downloading it ever again. So the download function should
not return the xarray. Even though the download may take hours so it
does not make sense from this point of view.

src/feedinlib/cds_request_tools.py

@@ -14,7 +14,6 @@
 def _get_cds_data(
     dataset_name="reanalysis-era5-single-levels",
     target_file=None,
-    chunks=None,
     cds_client=None,
     **cds_params,
 ):
@@ -32,13 +31,10 @@ def _get_cds_data(
         'Show API request', the short name is the string on the 6th line
         after 'c.retrieve('
     :param target_file: (str) name of the file to save downloaded locally
-    :param chunks: (dict)
     :param cds_client: handle to CDS client (if none is provided, then it is
         created)
     :param cds_params: (dict) parameter to pass to the CDS request
 
-    :return: CDS data in an xarray format
-
     """
 
     # https://cds.climate.copernicus.eu/api-how-to
@@ -102,18 +98,6 @@ def _get_cds_data(
     # Download the data in the target file
     result.download(target_file)
 
-    # Extract the data from the target file
-    answer = xr.open_dataset(target_file, chunks=chunks)
-
-    # Now that the data has been extracted the file path is removed if it was
-    # not provided. This will currently not work on windows if the dataset is
-    # too large as the file will be locked by the reading process.
-    if no_target_file_provided is True:
-        os.unlink(target_file)
-
-    # Here yield might be preferable in case of large datasets
-    return answer
-
 
 def _format_cds_request_datespan(start_date, end_date):
     """
@@ -319,7 +303,6 @@ def get_cds_data_from_datespan_and_position(
         after 'c.retrieve('
     :param target_file: (str) name of the file in which downloading the data
         locally
-    :param chunks: (dict)
     :param cds_client: handle to CDS client (if none is provided, then it is
         created)
     :param cds_params: (dict) parameter to pass to the CDS request

src/feedinlib/era5.py

@@ -10,12 +10,11 @@
 def get_era5_data_from_datespan_and_position(
     start_date,
     end_date,
+    target_file,
     variable="feedinlib",
     latitude=None,
     longitude=None,
     grid=None,
-    target_file=None,
-    chunks=None,
     cds_client=None,
 ):
     """
@@ -38,7 +37,6 @@ def get_era5_data_from_datespan_and_position(
         resolutions in deg. It needs to be an integer fraction of 90 deg.
     :param target_file: (str) name of the file in which to store downloaded
         data locally
-    :param chunks: (dict)
     :param cds_client: handle to CDS client (if none is provided, then it is
         created)
     :return: CDS data in an xarray format