write control data section to a file
        
        Parameters
        ----------
        f: file handle or string filename

def write(self,f):
        """ write control data section to a file
        
        Parameters
        ----------
        f: file handle or string filename

        """
        if isinstance(f,str):
            f = open(f,'w')
            f.write("pcf\n")
            f.write("* control data\n")
        for line in CONTROL_VARIABLE_LINES:
            [f.write(self.formatted_values[name.replace('[','').replace(']','')]) for name in line.split()]
            f.write('\n')