Validate the initial centers.

    Parameters
    ----------
    initial_centers : SFrame
        Initial cluster center locations, in SFrame form.

def _validate_initial_centers(initial_centers):
    """
    Validate the initial centers.

    Parameters
    ----------
    initial_centers : SFrame
        Initial cluster center locations, in SFrame form.
    """
    if not (isinstance(initial_centers, _SFrame)):
        raise TypeError("Input 'initial_centers' must be an SFrame.")

    if initial_centers.num_rows() == 0 or initial_centers.num_columns() == 0:
        raise ValueError("An 'initial_centers' argument is provided " +
                         "but has no data.")