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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 build_schema(self, fields):
 """ Build the schema from fields. :param fields: A list of fields in the index :returns: list of dictionaries Each dictionary has the keys field_name: The name of the field index type: what type of value it is 'multi_valued': if it allows more than one value 'column': a number identifying it 'type': the type of the field 'multi_valued': 'false', 'column': 0} """

        content_field_name = ''
        schema_fields = [
            {'field_name': ID,
             'type': 'text',
             'multi_valued': 'false',
             'column': 0},
            {'field_name': DJANGO_ID,
             'type': 'integer',
             'multi_valued': 'false',
             'column': 1},
            {'field_name': DJANGO_CT,
             'type': 'text',
             'multi_valued': 'false',
             'column': 2},
        ]
        self._columns[ID] = 0
        self._columns[DJANGO_ID] = 1
        self._columns[DJANGO_CT] = 2

        column = len(schema_fields)

        for field_name, field_class in sorted(list(fields.items()), key=lambda n: n[0]):
            if field_class.document is True:
                content_field_name = field_class.index_fieldname

            if field_class.indexed is True:
                field_data = {
                    'field_name': field_class.index_fieldname,
                    'type': 'text',
                    'multi_valued': 'false',
                    'column': column,
                }

                if field_class.field_type == 'date':
                    field_data['type'] = 'date'
                elif field_class.field_type == 'datetime':
                    field_data['type'] = 'datetime'
                elif field_class.field_type == 'integer':
                    field_data['type'] = 'integer'
                elif field_class.field_type == 'float':
                    field_data['type'] = 'float'
                elif field_class.field_type == 'boolean':
                    field_data['type'] = 'boolean'
                elif field_class.field_type == 'ngram':
                    field_data['type'] = 'ngram'
                elif field_class.field_type == 'edge_ngram':
                    field_data['type'] = 'edge_ngram'

                if field_class.is_multivalued:
                    field_data['multi_valued'] = 'true'

                schema_fields.append(field_data)
                self._columns[field_data['field_name']] = column
                column += 1

        return content_field_name, schema_fields