getDirectiveSource method
Implementation
ProviderSource? getDirectiveSource(CompileDirectiveMetadata? directive) =>
    directive != null
        ? _providers.get(identifierToken(directive.type))
        : null;ProviderSource? getDirectiveSource(CompileDirectiveMetadata? directive) =>
    directive != null
        ? _providers.get(identifierToken(directive.type))
        : null;