feat(yaml): add support for multi-documents YAML files

from typing import Any, Dict, List, Optional

# Modules libraries

from yaml import dump as yaml_dump, load as yaml_load

from yaml import dump as yaml_dump, load_all as yaml_load_all

from yaml import SafeLoader as yaml_SafeLoader, YAMLError as yaml_Error

from yaml.nodes import SequenceNode as yaml_SequenceNode

        # Variables

        data: Optional[YAML.Data]

        documents: List[YAML.Data]

        # Prepare loader class

        loader = yaml_SafeLoader

        loader.add_constructor(YAML.Reference.TAG, YAML.Reference.add_constructor)

        # Load YAML data

        data = yaml_load(stream, Loader=loader)

        # Load YAML documents

        documents = list(yaml_load_all(stream, Loader=loader))

        # Acquire YAML configuration data

        if len(documents) == 1:

            data = documents[0]

        # Empty YAML data

        elif len(documents) == 0:

            data = {}

        # Unsupport YAML data

        else:

            data = documents[-1]

        # Result

        return data