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import re
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from abc import ABC, abstractmethod
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import json
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import dateutil.parser
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def _type_to_snake_case(type_):
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return re.sub(r'(?<!^)(?=[A-Z])', '_', type_.__name__).lower()
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class BaseSerializer(ABC):
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type_ = None
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def __init__(self, obj):
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if isinstance(obj, self.type_):
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self.obj = obj
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elif isinstance(obj, (str, dict)):
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self.obj = self.to_object(obj)
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else:
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raise TypeError('The "{}" object must be {}, str or dict, not {!r}.'
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.format(_type_to_snake_case(self.type_), self.type_.__name__, obj.__class__.__name__))
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def get_object(self):
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return self.obj
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def get_json(self):
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return self.to_json(self.obj)
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@staticmethod
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def _remove_empty_values(data):
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return {k: v for k, v in data.items() if v is not None}
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@classmethod
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def to_json(cls, obj):
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cls.ensure_type(obj)
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return cls._to_json(obj)
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@staticmethod
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@abstractmethod
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def _to_json(obj):
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pass
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@classmethod
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def to_object(cls, json_):
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json_ = cls.ensure_dict(json_)
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return cls._to_object(json_)
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@staticmethod
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@abstractmethod
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def _to_object(json_):
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pass
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@staticmethod
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def ensure_dict(json_):
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if not isinstance(json_, (str, dict)):
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raise TypeError('The json object must be str or dict, not {!r}'.format(json_.__class__.__name__))
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if isinstance(json_, str):
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return json.loads(json_)
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else:
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return json_
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@classmethod
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def ensure_type(cls, obj):
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if not isinstance(obj, cls.type_):
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raise TypeError('The object must be {}, not {!r}.'.format(cls.type_, obj.__class__.__name__))
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def __init_subclass__(cls, **kwargs):
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"""Checks that "type_" is defined and that name of the argument in subclasses __init__ method is the name of
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the "type_" in lowercase. It ensures that error in __init__ function of BaseSerializer has a correct message.
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"""
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if cls.type_ is None:
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raise AssertionError('Subclass of BaseSerializer has to define class "type_" that is being serialized.')
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if cls.__init__.__code__.co_varnames != ('self', _type_to_snake_case(cls.type_)):
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raise AssertionError('Argument of the __init__ method has to have a name "{}".'
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.format(_type_to_snake_case(cls.type_)))
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@staticmethod
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def _get_datetime_from_string(s):
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return dateutil.parser.parse(s)
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