def METHOD_NAME(sel, mat=None, eqsys=None):
    """
    Matplotlib cursor format for spy() on sparse matrices.
    """
    c, r = sel.target
    sr = 'Row: {:d}'.format(int(r))
    sc = 'Col: {:d}'.format(int(c))
    if eqsys is not None:
        sr += ' ({})'.format(eqsys[r].toxstring(r))
        sc += ' ({})'.format(eqsys[c].toxstring(c))
    s = sr + '\n' + sc
    if mat is not None:
        sv = 'Val: {:.4e}'.format(mat[r,c])
        s += '\n' + sv
    sel.annotation.set_text(s)