def build_function_header(function_name):
    """
        Build a header for a function. 

        args:
            function_name: the name of our function.
    """
    function_name = function_name.strip()
    num_char      = len(function_name)
    header        = function_name + '\n'
    header       += "-"*num_char + '\n\n'
    return header