Get mapping for single field schema.

        :param schema: field schema

def _get_field_mapping(self, schema):
        """Get mapping for single field schema.

        :param schema: field schema
        """
        if 'mapping' in schema:
            return schema['mapping']
        elif schema['type'] == 'dict' and 'schema' in schema:
            return self._get_mapping(schema['schema'])
        elif schema['type'] == 'list' and 'schema' in schema.get('schema', {}):
            return self._get_mapping(schema['schema']['schema'])
        elif schema['type'] == 'datetime':
            return {'type': 'date'}
        elif schema['type'] == 'string' and schema.get('unique'):
            return {'type': 'string', 'index': 'not_analyzed'}