genvalues (1
    of the maximum real part). Either the matrix is not PSD, or there was
    an issue while computing the eigendecomposition of the matrix.
>>> _check_psd_eigenvalues([5, 5e-5j])  # insignificant imag part
array([5., 0.])
>>> _check_psd_eigenvalues([-5, -1])    # all negative
Traceback (most recent call last):
    ...
ValueError: All eigenvalues are negative (maximum is -1). Either the
    matrix is not PSD, or there was an issue while computing the
    eigendecomposition of the matrix.
>>> _check_psd_eigenvalues([5, -1])     # significant negative
Traceback (most recent call last):
    ...
ValueError: There are significant negative eigenvalues (0.2 of the
    maximum positive). Either the matrix is not PSD, or there was an issue
    while computing the eigendecomposition of the matrix.
>>> _check_psd_eigenvalues([5, -5e-5])  # insignificant negative
array([5., 0.])
>>> _check_psd_eigenvalues([5, 4e-12])  # bad conditioning (too small)
array([5., 0.])

gñh㈵øä>g{