Ability to save drawings

- Added `toolbox` to the common methods.
- `toolbox.save_drawings_under` can save drawings under a specific `topbar` widget. eg `chart.toolbox.save_drawings_under(chart.topbar[’symbol’]`)
- `toolbox.load_drawings` will load and display drawings stored under the tag/string given.
- `toolbox.export_drawings` will export all currently saved drawings to the given file path.
- `toolbox.import_drawings` will import the drawings stored at the given file path.

Fixes/Enhancements:
- `update` methods are no longer case sensitive.
- HorizontalLines no longer throw cyclic structure errors in the web console.
- `API` methods can now be normal methods or coroutines.

lightweight_charts/abstract.py

@@ -1,3 +1,4 @@
+import json
 import os
 from datetime import timedelta, datetime
 from base64 import b64decode
@@ -59,23 +60,35 @@ class SeriesCommon:
             }}
         ''')
 
+    @staticmethod
+    def _rename(data, mapper, is_dataframe):
+        if is_dataframe:
+            data.columns = [mapper[key] if key in mapper else key for key in data.columns]
+        else:
+            data.index = [mapper[key] if key in mapper else key for key in data.index]
+
     def _df_datetime_format(self, df: pd.DataFrame, exclude_lowercase=None):
         df = df.copy()
-        df.columns = df.columns.str.lower()
-        if exclude_lowercase:
-            df[exclude_lowercase] = df[exclude_lowercase.lower()]
+        if 'date' not in df.columns and 'time' not in df.columns:
+            df.columns = df.columns.str.lower()
+            if exclude_lowercase:
+                df[exclude_lowercase] = df[exclude_lowercase.lower()]
         if 'date' in df.columns:
-            df = df.rename(columns={'date': 'time'})
+            self._rename(df, {'date': 'time'}, True)
         elif 'time' not in df.columns:
             df['time'] = df.index
         self._set_interval(df)
         df['time'] = self._datetime_format(df['time'])
         return df
 
-    def _series_datetime_format(self, series):
+    def _series_datetime_format(self, series: pd.Series, exclude_lowercase=None):
         series = series.copy()
-        if 'date' in series.keys():
-            series = series.rename({'date': 'time'})
+        if 'date' not in series.index and 'time' not in series.index:
+            series.index = series.index.str.lower()
+            if exclude_lowercase:
+                self._rename(series, {exclude_lowercase.lower(): exclude_lowercase}, False)
+        if 'date' in series.index:
+            self._rename(series, {'date': 'time'}, False)
         series['time'] = self._datetime_format(series['time'])
         return series
 
@@ -353,6 +366,47 @@ class TopBar:
                 return widget
 
 
+class ToolBox:
+    def __init__(self, chart):
+        self.run_script = chart.run_script
+        self.id = chart.id
+        self._return_q = chart._return_q
+
+        self._saved_drawings = {}
+
+    def save_drawings_under(self, widget: Widget):
+        """
+        Drawings made on charts will be saved under the widget given. eg `chart.toolbox.save_drawings_under(chart.topbar['symbol'])`.
+        """
+        self._save_under = widget
+
+    def load_drawings(self, tag: str):
+        """
+        Loads and displays the drawings on the chart stored under the tag given.
+        """
+        if not self._saved_drawings.get(tag):
+            return
+        self.run_script(f'if ("toolBox" in {self.id}) {self.id}.toolBox.loadDrawings({json.dumps(self._saved_drawings[tag])})')
+
+    def import_drawings(self, file_path):
+        """
+        Imports a list of drawings stored at the given file path.
+        """
+        with open(file_path, 'r') as f:
+            json_data = json.load(f)
+            self._saved_drawings = json_data
+
+    def export_drawings(self, file_path):
+        """
+        Exports the current list of drawings to the given file path.
+        """
+        with open(file_path, 'w+') as f:
+            json.dump(self._saved_drawings, f)
+
+    def _save_drawings(self, drawings):
+        self._saved_drawings[self._save_under.value] = json.loads(drawings)
+
+
 class LWC(SeriesCommon):
     def __init__(self, volume_enabled: bool = True, inner_width: float = 1.0, inner_height: float = 1.0, dynamic_loading: bool = False,
                  scale_candles_only: bool = False, topbar: bool = False, searchbox: bool = False, toolbox: bool = False,
@@ -394,6 +448,7 @@ class LWC(SeriesCommon):
         if toolbox:
             self.run_script(JS['toolbox'])
             self.run_script(f'{self.id}.toolBox = new ToolBox({self.id})')
+            self.toolbox: ToolBox = ToolBox(self)
         if not topbar and not searchbox:
             return
         self.run_script(JS['callback'])