Implement base MissingValues strategies

frontend/pages/normalization.py

@@ -0,0 +1,23 @@
+import streamlit as st
+from mvstrategy import MVStrategy
+
+if "data" in st.session_state:
+    data = st.session_state.data
+    st.session_state.data = data.copy()
+
+    for column, series in data.items():
+        missing_count = series.isna().sum()
+        choices = MVStrategy.list_available(series)
+        option = st.selectbox(
+            f"Missing values of {column} ({missing_count})",
+            choices,
+            index=1,
+            key=f"mv-{column}",
+        )
+        # Always re-get the series to avoid reusing an invalidated series pointer
+        data = option.apply(data, column, data[column])
+
+    st.write(data)
+    st.session_state.working_data = data
+else:
+    st.error("file not loaded")

frontend/pages/visualization.py

@@ -5,8 +5,8 @@ import seaborn as sns
 st.header("Data Visualization")
 
 
-if "data" in st.session_state:
-    data = st.session_state.data
+if "working_data" in st.session_state:
+    data = st.session_state.working_data
 
     st.subheader("Histogram")
     column_to_plot = st.selectbox("Select Column for Histogram", data.columns)