def __add__(self, other):
if isinstance(other, FormulaElement):<EOL><INDENT>if self == other:<EOL><INDENT>return Formula({self: <NUM_LIT:2>})<EOL><DEDENT>return Formula({self: <NUM_LIT:1>, other: <NUM_LIT:1>})<EOL><DEDENT>return NotImplemented<EOL>
Add formula elements creating subformulas