Move SoundingSample type annotations into __init__()

lib/xmet/sounding.py

@@ -23,23 +23,21 @@ class SoundingSample(DatabaseTable):
         'dewpoint', 'wind_dir', 'wind_speed'
     )
 
-    id:          int
-    sounding_id: int
-    elapsed:     int
-    pressure:    float
-    pressure_qa: str
-    height:      float
-    height_qa:   str
-    temp:        float
-    temp_qa:     str
-    humidity:    float
-    dewpoint:    float
-    wind_dir:    float
-    wind_speed:  float
-
     def __init__(self):
         super().__init__()
-        self.id = None
+        self.id: int = None
+        self.sounding_id: int   = None
+        self.elapsed:     int   = None
+        self.pressure:    float = None
+        self.pressure_qa: str   = None
+        self.height:      float = None
+        self.height_qa:   str  = None
+        self.temp:        float = None
+        self.temp_qa:     str   = None
+        self.humidity:    float = None
+        self.dewpoint:    float = None
+        self.wind_dir:    float = None
+        self.wind_speed:  float = None
 
     def is_saturated(self) -> bool:
         return self.humidity >= 100.0