api.v0alpha.FieldMetadata(FieldMetadata)

{
    "time_format": "string",
    "precision": "DATETIME_PRECISION_NOW",
    "remove_characters": "string",
    "replace_empty": "string",
    "replace_error": "string",
    "remove_letters": true,
    "remove_numbers": true,
    "remove_symbols": true,
    "leave_characters": "string",
    "remove_string": "string",
    "json_dot_path": "string",
    "json_force_type_match": true,
    "starting_position": 0,
    "field_length": 0
}