Standardise style of kwargs

  - Use Optional[Dict] for all third-party libraries kwargs
  - Code review for ioos#280

  Co-authored-by: Filipe <ocefpaf@gmail.com>
  Co-authored-by: Alex Kerney <abk@mac.com>

erddapy/core/interfaces.py

@@ -17,13 +17,11 @@
     import xarray as xr
     from netCDF4 import Dataset
 
-<<<<<<< HEAD
-def to_pandas(url: str, requests_kwargs: Optional[Dict] = None, **kw) -> "pd.DataFrame":
-=======
 def to_pandas(
-    url: str, requests_kwargs: Optional[Dict] = None, **pandas_kwargs
-) -> pd.DataFrame:
->>>>>>> bf7cbb2 (Renaming **kw according to each library)
+    url: str,
+    requests_kwargs: Optional[Dict] = None,
+    pandas_kwargs: Optional[Dict] = None,
+) -> "pd.DataFrame":
     """
     Convert a URL to Pandas DataFrame.
 
@@ -33,30 +31,27 @@ def to_pandas(
     """
     if requests_kwargs is None:
         requests_kwargs = {}
+    if pandas_kwargs is None:
+        pandas_kwargs = {}
     data = urlopen(url, **requests_kwargs)
     try:
         return pd.read_csv(data, **pandas_kwargs)
     except Exception as e:
         raise ValueError(f"Could not read url {url} with Pandas.read_csv.") from e
 
 
-<<<<<<< HEAD
-def to_ncCF(url: str, protocol: str = None, **kw) -> "Dataset":
-    """Convert a URL to a netCDF4 Dataset."""
-=======
 def to_ncCF(
     url: str,
     protocol: str = None,
     requests_kwargs: Optional[Dict] = None,
-) -> Dataset:
+) -> "Dataset":
     """
     Convert a URL to a netCDF4 Dataset.
 
     url: URL to request data from.
     protocol: 'griddap' or 'tabledap'.
     requests_kwargs: arguments to be passed to urlopen method (including auth).
     """
->>>>>>> bf7cbb2 (Renaming **kw according to each library)
     if protocol == "griddap":
         raise ValueError(
             f"Cannot use .ncCF with griddap protocol. The URL you tried to access is: '{url}'.",
@@ -70,28 +65,34 @@ def to_xarray(
     url: str,
     response="opendap",
     requests_kwargs: Optional[Dict] = None,
-    **xarray_kwargs,
+    xarray_kwargs: Optional[Dict] = None,
 ) -> "xr.Dataset":
     """
     Convert a URL to an xarray dataset.
 
     url: URL to request data from.
     response: type of response to be requested from the server.
-    requests_kwargs: arguments to be passed to urlopen method
+    requests_kwargs: arguments to be passed to urlopen method.
     xarray_kwargs: kwargs to be passed to third-party library (xarray).
     """
     import xarray as xr
 
     if requests_kwargs is None:
         requests_kwargs = {}
+    if xarray_kwargs is None:
+        xarray_kwargs = {}
     if response == "opendap":
         return xr.open_dataset(url, **xarray_kwargs)
     else:
         nc = _nc_dataset(url, **requests_kwargs)
         return xr.open_dataset(xr.backends.NetCDF4DataStore(nc), **xarray_kwargs)
 
 
-def to_iris(url: str, requests_kwargs: Optional[Dict] = None, **iris_kwargs):
+def to_iris(
+    url: str,
+    requests_kwargs: Optional[Dict] = None,
+    iris_kwargs: Optional[Dict] = None,
+):
     """
     Convert a URL to an iris CubeList.
 
@@ -103,6 +104,8 @@ def to_iris(url: str, requests_kwargs: Optional[Dict] = None, **iris_kwargs):
 
     if requests_kwargs is None:
         requests_kwargs = {}
+    if iris_kwargs is None:
+        iris_kwargs = {}
     data = urlopen(url, **requests_kwargs)
     with _tempnc(data) as tmp:
         cubes = iris.load_raw(tmp, **iris_kwargs)