Fix: dbnomics.api_base_url ignored

README.md

@@ -38,7 +38,7 @@ dataframe = fetch_series(
 )
 ```
 
-Or set the default API URL by [monkey-patching](https://en.wikipedia.org/wiki/Monkey_patch) the `dbnomics` module, like this:
+Or globally change the default API URL used by the `dbnomics` module, like this:
 
 ```python
 import dbnomics

dbnomics/__init__.py

@@ -62,7 +62,7 @@ class TooManySeries(Exception):
 
 
 def fetch_series(provider_code=None, dataset_code=None, series_code=None, dimensions=None, series_ids=None,
-                 max_nb_series=None, api_base_url=default_api_base_url,
+                 max_nb_series=None, api_base_url=None,
                  editor_api_base_url=default_editor_api_base_url, filters=None):
     """Download time series from DBnomics. Filter series by different ways according to the given parameters.
 
@@ -108,6 +108,9 @@ def fetch_series(provider_code=None, dataset_code=None, series_code=None, dimens
       fetch_series('AMECO/ZUTN/EA19.1.0.0.0.ZUTN', filters=[{"code": "interpolate", "parameters": {"frequency": "monthly", "method": "spline"}}])
     """
     # Parameters validation
+    global default_api_base_url
+    if api_base_url is None:
+        api_base_url = default_api_base_url
     if not api_base_url.endswith('/'):
         api_base_url += "/"
     if dataset_code is None: