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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 list_field_append(doc, field, value):
 """ Appends a value to a list field in a locally cached Document object. If a field does not exist it will be created first. :param Document doc: Locally cached Document object that can be a Document, DesignDocument or dict. :param str field: Name of the field list to append to. :param value: Value to append to the field list. """

        if doc.get(field) is None:
            doc[field] = []
        if not isinstance(doc[field], list):
            raise CloudantDocumentException(102, field)
        if value is not None:
            doc[field].append(value)