Fix: Change None values to NaN in combine_first method for better handling of missing data

Author: Lavishgangwani

pandas/core/series.py

@@ -3223,6 +3223,14 @@ def combine_first(self, other) -> Series:
         dtype: float64
         """
         from pandas.core.reshape.concat import concat
+	    
+        # Change None values to NaN for both Series
+        def replace_none_with_nan(series):
+            series.fillna(value=np.nan, inplace=True)
+
+        # Apply the function to both Series
+        replace_none_with_nan(self)
+        replace_none_with_nan(other)  # Removed the extra parenthesis here
 
         if self.dtype == other.dtype:
             if self.index.equals(other.index):