def get_pycallgraph_str(i_args,out_png):
    """
    Get caller to pycallgraph.
    
    Parameters
    ----------
     i_args : str
         generated wit get_include_functions().
     out_png : str
         output image (.png).
     
    Returns
    -------
     pycallgraph_str : str
         caller.
    """
    pycallgraph_str = "pycallgraph "+i_args+"graphviz -o "+out_png+" -- "
    return(pycallgraph_str)