Changed variable table to simplify the function calls

src/main/java/python/interpreter/value/VariableTable.java

@@ -5,14 +5,14 @@ import java.util.Map;
 import java.util.Optional;
 
 public class VariableTable {
-    Map<String, PythonValue> variables = new HashMap<>();
+    Map<String, PythonValue> globalVariables = new HashMap<>();
 
     public void assignVariable(String variableName, PythonValue value) {
-        variables.put(variableName, value);
+        globalVariables.put(variableName, value);
     }
 
     public Optional<PythonValue> getVariableValue(String variableName) {
-        PythonValue value = variables.get(variableName);
+        PythonValue value = globalVariables.get(variableName);
         if (value != null) {
             return Optional.of(value);
         }