<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _parse_schema_resource(info):
 """Parse a resource fragment into a schema field. Args: info: (Mapping[str->dict]):
 should contain a "fields" key to be parsed Returns: (Union[Sequence[:class:`google.cloud.bigquery.schema.SchemaField`],None]) a list of parsed fields, or ``None`` if no "fields" key found. """

    if "fields" not in info:
        return ()

    schema = []
    for r_field in info["fields"]:
        name = r_field["name"]
        field_type = r_field["type"]
        mode = r_field.get("mode", "NULLABLE")
        description = r_field.get("description")
        sub_fields = _parse_schema_resource(r_field)
        schema.append(SchemaField(name, field_type, mode, description, sub_fields))
    return schema