add helper fn to get bool from bool, int or str

The config file will supply all as str, so such a function will be useful
For example, this commit also modifies the Sonde class to import helper
and use this new function to check for the value of the skip argument by first
converting the config provided value to bool.

src/halodrops/helper/__init__.py

@@ -0,0 +1,17 @@
+def get_bool(s):
+    if isinstance(s, bool):
+        return s
+    elif isinstance(s, int):
+        return bool(s)
+    elif isinstance(s, str):
+        lower_s = s.lower()
+        if lower_s == "true":
+            return True
+        elif lower_s == "false":
+            return False
+        elif lower_s in ["0", "1"]:
+            return bool(int(lower_s))
+        else:
+            raise ValueError(f"Cannot convert {s} to boolean")
+    else:
+        raise ValueError(f"Cannot convert {s} to boolean")

src/halodrops/sonde.py

@@ -6,6 +6,7 @@
 import xarray as xr
 
 from halodrops.helper import rawreader as rr
+import halodrops.helper as hh
 
 _no_default = object()
 
@@ -233,7 +234,7 @@ def weighted_fullness(
         float
             Fraction of non-nan variable values along time_dimension weighed for sampling frequency
         """
-        if skip:
+        if hh.get_bool(skip):
             return self
         else:
             for variable, sampling_frequency in variable_dict.items():
@@ -276,7 +277,7 @@ def near_surface_coverage(
         ValueError
             If the attribute `aspen_ds` does not exist.
         """
-        if skip:
+        if hh.get_bool(skip):
             return self
         else:
             if not hasattr(self, "aspen_ds"):