Implement follow_dewpoint()

lib/xmet/sounding.py

@@ -185,6 +185,14 @@ class Sounding(DatabaseTable):
 
         return series
 
+    def follow_dewpoint(self) -> Series:
+        series = Series()
+
+        for sample in self.samples:
+            series[sample.pressure] = sample.dewpoint
+
+        return series
+
 def between(n, a, b):
     return n > a and n < b