extract the data of the content and return it as a dictionary

def to_dict(self):
        """ extract the data of the content and return it as a dictionary
        """

        # 1. extract the schema fields
        data = self.extract_fields()

        # 2. include custom key-value pairs listed in the mapping dictionary
        for key, attr in self.attributes.iteritems():
            if key in self.ignore:
                continue  # skip ignores
            # fetch the mapped attribute
            value = getattr(self.context, attr, None)
            if value is None:
                value = getattr(self, attr, None)
            # handle function calls
            if callable(value):
                value = value()
            # map the value to the given key from the mapping
            data[key] = api.to_json_value(self.context, key, value)
        return data