def Rules(**rules):
for (lhs, rhs) in list(rules.items()):<EOL><INDENT>rules[lhs] = [alt.strip().split() for alt in rhs.split('<STR_LIT:|>')]<EOL><DEDENT>return rules<EOL>
Create a dictionary mapping symbols to alternative sequences.
    >>> Rules(A = "B C | D E")
    {'A': [['B', 'C'], ['D', 'E']]}