Fix bad _bnds existence check and remove .keys() references

Fixes issue in `get_bnds()` where the existence of `lat_bounds` instead of `lat_bnds` (the `xa.fix_ds()` convention) was checked for

xagg/aux.py

@@ -111,15 +111,15 @@ def fix_ds(ds,var_cipher = {'latitude':{'latitude':'lat','longitude':'lon'},
 
     # List of variables that represent bounds
     if type(ds) == xr.core.dataset.Dataset:
-        bnd_vars = [k for k in list(ds.keys()) if 'bnds' in k]
+        bnd_vars = [k for k in list(ds) if 'bnds' in k]
     elif type(ds) == xr.core.dataarray.DataArray:
         bnd_vars = []
     else:
         raise TypeError('[ds] needs to be an xarray structure (Dataset or DataArray).')
 
     # Fix lat/lon variable names (sizes instead of dims to be compatible with both ds, da...)
-    if 'lat' not in ds.sizes.keys():
-        test_dims = [k for k in var_cipher.keys() if k in ds.sizes.keys()]
+    if 'lat' not in ds.sizes:
+        test_dims = [k for k in var_cipher if k in ds.sizes]
         if len(test_dims) == 0:
             raise NameError('No valid lat/lon variables found in the dataset.')
         else:
@@ -156,7 +156,7 @@ def fix_ds(ds,var_cipher = {'latitude':{'latitude':'lat','longitude':'lon'},
     if (type(ds) == xr.core.dataset.Dataset):
         # Three if statements because of what I believe to be a jupyter error
         # (where all three statements are evaluated instead of one at a time)
-        if ('lon_bnds' in ds.keys()):
+        if ('lon_bnds' in ds):
             if (ds.lon_bnds.max()>180):
                 ds['lon_bnds'] = (ds['lon_bnds'] + 180) % 360 - 180
 
@@ -241,11 +241,13 @@ def get_bnds(ds,wrap_around_thresh='dynamic',
         # honestly, it *may* already work by just changing edges['lon']
         # to [0,360], but it's not tested yet. 
 
-    if ('lat' not in ds.keys()) | ('lon' not in ds.keys()):
+    if ('lat' not in ds) | ('lon' not in ds):
         raise KeyError('"lat"/"lon" not found in [ds]. Make sure the '+
                        'geographic dimensions follow this naming convention (e.g., run `xa.fix_ds(ds)` before inputting.')
 
-    if 'lat_bounds' in ds.keys():
+    if ('lat_bnds' in ds) and (`lon_bnds` in ds):
+        # `xa.fix_ds()` should rename bounds to `lat/lon_bnds`
+        # If bounds present, do nothing
         return ds
     else:
         if not silent:
@@ -388,12 +390,12 @@ def subset_find(ds0,ds1):
     
     """
 
-    if 'loc' not in ds0.sizes.keys():
+    if 'loc' not in ds0.sizes:
         ds0 = ds0.stack(loc = ('lat','lon'))
         was_stacked = True
     else:
         was_stacked = False
-    #if 'loc' not in ds1.sizes.keys():
+    #if 'loc' not in ds1.sizes:
     #    ds1 = ds1.stack(loc = ('lat','lon'))
 
     # Need a test to make sure the grid is the same. So maybe the gdf_out class