def _get_col_type_dict(self):
        """
        
        """
        schema = []
        if isinstance(self.schema, string_types):
            schema = json.loads(self.schema)
        elif isinstance(self.schema, list):
            schema = self.schema
        elif self.schema is not None:
            self.log.warn('Using default schema due to unexpected type.'
                          'Should be a string or list.')

        col_type_dict = {}
        try:
            col_type_dict = {col['name']: col['type'] for col in schema}
        except KeyError:
            self.log.warn('Using default schema due to missing name or type. Please '
                          'refer to: https://cloud.google.com/bigquery/docs/schemas'
                          '#specifying_a_json_schema_file')
        return col_type_dict