matrix.
  * **X** (*tensor**, **optional*) -- the input tensor of size (*,
    m, n) where *k <= n <= m*. When specified, it is used as
    initial approximation of eigenvectors. X must be a dense
    tensor.

  * **iK** (*tensor**, **optional*) -- the input tensor of size
    (*, m, m). When specified, it will be used as preconditioner.

  * **k** (*integer**, **optional*) -- the number of requested
    eigenpairs. Default is the number of X columns (when
    specified) or *1*.

  * **n** (*integer**, **optional*) -- if X is not specified then
    *n* specifies the size of the generated random approximation
    of eigenvectors. Default value for *n* is *k*. If X is
    specified, the value of *n* (when specified) must be the
    number of X columns.

  * **tol** (*float**, **optional*) -- residual tolerance for
    stopping criterion. Default is *feps ** 0.5* where *feps* is
