Flutter expected a key while parsing a block mapping

Question

Here is pubspec.yaml

dependencies:
    flutter:
        sdk: flutter
      # The following adds the Cupertino Icons font to your application.
      # Use with the CupertinoIcons class for iOS style icons.
      url_launcher: ^4.0.3
      cupertino_icons: ^0.1.2

Error on line 20, column 3 of pubspec.yaml: Expected a key while parsing a block mapping.I am getting this error when i try to implement phone call in my app.Here the line 20 is url_launcher: ^4.0.3