This method finds a schema known to Flasgger and returns it.

        :raise KeyError: when the specified :param schema_id: is not
        found by Flasgger

        :param schema_id: the id of the desired schema

def get_schema(self, schema_id):
        """
        This method finds a schema known to Flasgger and returns it.

        :raise KeyError: when the specified :param schema_id: is not
        found by Flasgger

        :param schema_id: the id of the desired schema
        """
        schema_specs = get_schema_specs(schema_id, self)

        if schema_specs is None:
            raise KeyError(
                'Specified schema_id \'{0}\' not found'.format(schema_id))

        for schema in (
                parameter.get('schema') for parameter in
                schema_specs['parameters']):
            if schema is not None and schema.get('id').lower() == schema_id:
                return schema