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[EDIT] FILE: serializer.py

__all__ = ['Serializer', 'SerializerError']

from .error import YAMLError
from .events import *
from .nodes import *

class SerializerError(YAMLError):
    pass

class Serializer:

ANCHOR_TEMPLATE = 'id%03d'

def __init__(self, encoding=None,
            explicit_start=None, explicit_end=None, version=None, tags=None):
        self.use_encoding = encoding
        self.use_explicit_start = explicit_start
        self.use_explicit_end = explicit_end
        self.use_version = version
        self.use_tags = tags
        self.serialized_nodes = {}
        self.anchors = {}
        self.last_anchor_id = 0
        self.closed = None

def open(self):
        if self.closed is None:
            self.emit(StreamStartEvent(encoding=self.use_encoding))
            self.closed = False
        elif self.closed:
            raise SerializerError("serializer is closed")
        else:
            raise SerializerError("serializer is already opened")

def close(self):
        if self.closed is None:
            raise SerializerError("serializer is not opened")
        elif not self.closed:
            self.emit(StreamEndEvent())
            self.closed = True

#def __del__(self):
    #    self.close()

def serialize(self, node):
        if self.closed is None:
            raise SerializerError("serializer is not opened")
        elif self.closed:
            raise SerializerError("serializer is closed")
        self.emit(DocumentStartEvent(explicit=self.use_explicit_start,
            version=self.use_version, tags=self.use_tags))
        self.anchor_node(node)
        self.serialize_node(node, None, None)
        self.emit(DocumentEndEvent(explicit=self.use_explicit_end))
        self.serialized_nodes = {}
        self.anchors = {}
        self.last_anchor_id = 0

def anchor_node(self, node):
        if node in self.anchors:
            if self.anchors[node] is None:
                self.anchors[node] = self.generate_anchor(node)
        else:
            self.anchors[node] = None
            if isinstance(node, SequenceNode):
                for item in node.value:
                    self.anchor_node(item)
            elif isinstance(node, MappingNode):
                for key, value in node.value:
                    self.anchor_node(key)
                    self.anchor_node(value)

def generate_anchor(self, node):
        self.last_anchor_id += 1
        return self.ANCHOR_TEMPLATE % self.last_anchor_id

def serialize_node(self, node, parent, index):
        alias = self.anchors[node]
        if node in self.serialized_nodes:
            self.emit(AliasEvent(alias))
        else:
            self.serialized_nodes[node] = True
            self.descend_resolver(parent, index)
            if isinstance(node, ScalarNode):
                detected_tag = self.resolve(ScalarNode, node.value, (True, False))
                default_tag = self.resolve(ScalarNode, node.value, (False, True))
                implicit = (node.tag == detected_tag), (node.tag == default_tag)
                self.emit(ScalarEvent(alias, node.tag, implicit, node.value,
                    style=node.style))
            elif isinstance(node, SequenceNode):
                implicit = (node.tag
                            == self.resolve(SequenceNode, node.value, True))
                self.emit(SequenceStartEvent(alias, node.tag, implicit,
                    flow_style=node.flow_style))
                index = 0
                for item in node.value:
                    self.serialize_node(item, node, index)
                    index += 1
                self.emit(SequenceEndEvent())
            elif isinstance(node, MappingNode):
                implicit = (node.tag
                            == self.resolve(MappingNode, node.value, True))
                self.emit(MappingStartEvent(alias, node.tag, implicit,
                    flow_style=node.flow_style))
                for key, value in node.value:
                    self.serialize_node(key, node, None)
                    self.serialize_node(value, node, key)
                self.emit(MappingEndEvent())
            self.ascend_resolver()

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