smallest non-zero floating-point number of the given input
        tensor A data type.
  * **largest** (*bool**, **optional*) -- when True, solve the
    eigenproblem for the largest eigenvalues. Otherwise, solve the
    eigenproblem for smallest eigenvalues. Default is *True*.

  * **method** (*str**, **optional*) -- select LOBPCG method. See
    the description of the function above. Default is "ortho".

  * **niter** (*int**, **optional*) -- maximum number of
    iterations. When reached, the iteration process is hard-
    stopped and the current approximation of eigenpairs is
    returned. For infinite iteration but until convergence
    criteria is met, use *-1*.

  * **tracker** (*callable**, **optional*) --

    a function for tracing the iteration process. When specified,
    it is called at each iteration step with LOBPCG instance as an
    argument. The LOBPCG instance holds the full state of the
