def index(self, key):
        try:
            return self._keys.index(key)
        except ValueError:
            raise KeyError(key)
Calculate response surface equation coefficients using least squares regression.
dataset/ETHPy150Open nigelsmall/py2neo/py2neo/packages/neo4j/v1/session.py/Record.index--crossover with--dataset/ETHPy150Open OpenMDAO/OpenMDAO-Framework/openmdao.lib/src/openmdao/lib/surrogatemodels/response_surface.py/ResponseSurface.train