Check that the specified file looks like an image supported by PIL

def can_import(self, file_uris, current_doc=None):
        """
        Check that the specified file looks like an image supported by PIL
        """
        if len(file_uris) <= 0:
            return False
        for file_uri in file_uris:
            file_uri = self.fs.safe(file_uri)
            if not self.check_file_type(file_uri):
                return False
        return True