I cloned the repo, Installed required dependencies and created the API class as in the instructions. When I run the code for the first time I got the following Error:

"Install Android SDK Build-Tools 28.0.3 (revision: 28.0.3)" finished.
../../../AppData/Local/Pub/Cache/hosted/pub.dartlang.org/charts_flutter-0.10.0/lib/src/behaviors/legend/legend_entry_layout.dart:134:45: Error: The getter 'body1' isn't defined for the class 'TextTheme'.
 - 'TextTheme' is from 'package:flutter/src/material/text_theme.dart' ('/C:/src/flutter/packages/flutter/lib/src/material/text_theme.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named 'body1'.
      color ??= Theme.of(context).textTheme.body1.color;
                                            ^^^^^


FAILURE: Build failed with an exception.

* Where:
Script 'C:\src\flutter\packages\flutter_tools\gradle\flutter.gradle' line: 1070

* What went wrong:
Execution failed for task ':app:compileFlutterBuildDebug'.
> Process 'command 'C:\src\flutter\bin\flutter.bat'' finished with non-zero exit value 1

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 4m 0s
Exception: Gradle task assembleDebug failed with exit code 1


"Install Android SDK Build-Tools 28.0.3 (revision: 28.0.3)" finished.
../../../AppData/Local/Pub/Cache/hosted/pub.dartlang.org/charts_flutter-0.10.0/lib/src/behaviors/legend/legend_entry_layout.dart:134:45: Error: The getter 'body1' isn't defined for the class 'TextTheme'.
 - 'TextTheme' is from 'package:flutter/src/material/text_theme.dart' ('/C:/src/flutter/packages/flutter/lib/src/material/text_theme.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named 'body1'.
      color ??= Theme.of(context).textTheme.body1.color;
                                            ^^^^^


FAILURE: Build failed with an exception.

* Where:
Script 'C:\src\flutter\packages\flutter_tools\gradle\flutter.gradle' line: 1070

* What went wrong:
Execution failed for task ':app:compileFlutterBuildDebug'.
> Process 'command 'C:\src\flutter\bin\flutter.bat'' finished with non-zero exit value 1

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 4m 0s
Exception: Gradle task assembleDebug failed with exit code 1