tcl_asyncdelete async handler fix

Resolved an infrequent bug that occurred when there was a high volume of requests for the Matplotlib plot. The issue was related to a RuntimeError where the tcl_asyncdelete async handler was being deleted by an incorrect thread. Please refer to the following Stack Overflow thread for more information: https://stackoverflow.com/a/29172195.

src/CleanEmonBackend/API/API.py

@@ -1,27 +1,25 @@
 """This module defines the core functionality of the API"""
 
-import os
+
 from datetime import datetime
 from datetime import timedelta
 from io import BytesIO
-
-from typing import List
+from typing import Any
 from typing import Dict
+from typing import List, Optional
 from typing import Union
-from typing import Any
 
 from CleanEmonCore.models import EnergyData
 
-from .. import RES_DIR
 from CleanEmonBackend.lib.DBConnector import fetch_data
 from ..lib.DBConnector import adapter
-from ..lib.DBConnector import send_meta
-from ..lib.DBConnector import get_view_daily_consumption
 from ..lib.DBConnector import get_last_value
+from ..lib.DBConnector import get_view_daily_consumption
+from ..lib.DBConnector import send_meta
 from ..lib.plots import plot_data
 
 
-def get_data(date: str, from_cache: bool, sensors: List[str] = None, db: str = None, keep_last_only : bool = False) -> EnergyData:
+def get_data(date: Optional[str], from_cache: bool, sensors: List[str] = None, db: str = None, keep_last_only : bool = False) -> EnergyData:
     """Fetches and prepares the daily data that will be returned, filtering in the provided `sensors`.
     Note that there is no need to explicitly specify the "timestamp sensor", as it will always be included.
 

src/CleanEmonBackend/API/app_factory.py

@@ -364,7 +364,7 @@ def get_json_date_mean_consumption(dev_id: str = None, date: str = None, from_ca
             raise MissingMetadataField('Household m2')
         return res
 
-    @app.get("/dev_id/{dev_id}/meta/", tags=["Metadata"])
+    @app.get("/dev_id/{dev_id}/meta", tags=["Metadata"])
     @app.get("/dev_id/{dev_id}/meta/{field}", tags=["Metadata"])
     def get_json_meta(dev_id: str = None, field: str = None):
         """Returns the metadata for the current house.

src/CleanEmonBackend/lib/plots.py

@@ -3,7 +3,9 @@
 from io import BytesIO
 
 from typing import List
+import matplotlib
 
+matplotlib.use('svg')
 from matplotlib import pyplot as plt
 import pandas as pd
 import numpy as np