Dataframe commands (#3502)

* Sample command

* Join command with checks

* More dataframes commands

* Groupby and aggregate commands

* Missing feature dataframe flag

* Renamed file

* New commands for dataframes

* error parser and df reference

* filter command for dataframes

* removed name from nu_dataframe

* commands to save to parquet and csv

crates/nu-source/src/text.rs

@@ -11,9 +11,9 @@ use std::ops::Range;
 /// Used to represent the value of an input file.
 #[derive(Clone)]
 pub struct Text {
-    text: String,
-    start: usize,
-    end: usize,
+    pub text: String,
+    pub start: usize,
+    pub end: usize,
 }
 
 impl Text {