(self, formula, substitutions)
return substitutions.get(formula, formula)
Returns the substitution for formula, if one is defined, otherwise
        returns the formula unchanged.

        This is an helper function, to simplify the implementation of
        the walk_* functions.
Returns the substitution for formula, if one is defined, otherwise
        returns the formula unchanged.
Returns the substitution for formula if one is defined otherwise returns the formula unchanged .
def _substitute(self, formula, substitutions):
        """Returns the substitution for formula, if one is defined, otherwise
        returns the formula unchanged.

        This is an helper function, to simplify the implementation of
        the walk_* functions.
        """
        return substitutions.get(formula, formula)
def _substitute ( self , formula , substitutions ) : return substitutions . get ( formula , formula )