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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _format_fields(cls, declared_fields: typing.List[tuple]):
 """Process declared fields and construct a list of tuples that can be fed into dataclass constructor factory. """

        formatted_fields = []
        for declared_field in declared_fields:
            field_name = field_type = field_defn = None

            # Case when only (name), or "name", is specified
            if isinstance(declared_field, str) or len(declared_field) == 1:
                field_name = declared_field
                field_type = typing.Any
                field_defn = field(default=None)

            # Case when (name, type) are specified
            elif len(declared_field) == 2:
                field_name = declared_field[0]
                field_type = declared_field[1]
                field_defn = field(default=None)

            # Case when (name, type, field) are specified
            elif len(declared_field) == 3:
                field_name = declared_field[0]
                field_type = declared_field[1]

                # Process the definition and create a `field` object
                # Definition will be of the form `{'required': False, 'default': 'John'}`
                assert isinstance(declared_field[2], dict)
                metadata = default = None
                if 'required' in declared_field[2] and declared_field[2]['required']:
                    metadata = {'required': True}
                if 'default' in declared_field[2]:
                    default = declared_field[2]['default']
                field_defn = field(default=default, metadata=metadata)

            formatted_fields.append((field_name, field_type, field_defn))

        return formatted_fields