code: def evals(self):
          
          if self._evals is None:
              errMsg = "The metric eigenvalues have not been set in the "
              errMsg += "metricParameters instance."
              raise ValueError(errMsg)
          return self._evals
docs: The eigenvalues of the parameter space.
          This is a Dictionary of numpy.array
          Each entry in the dictionary corresponds to the different frequency
          ranges described in vary_fmax. If vary_fmax = False, the only entry
          will be f_upper, this corresponds to integrals in [f_low,f_upper). This
          entry is always present. Each other entry will use floats as keys to
          the dictionary. These floats give the upper frequency cutoff when it is
          varying.
          Each numpy.array contains the eigenvalues which, with the eigenvectors
          in evecs, are needed to rotate the
          coordinate system to one in which the metric is the identity matrix.