parameters: (p)
docstring: expression : '(' expression ')
docstring_summary: expression : '(' expression ')
docstring_tokens: expression : ( expression )
function: def p_expression_group(p):
      "expression : '(' expression ')'"
      p[0] = p[2]
function_tokens: def p_expression_group ( p ) : p [ 0 ] = p [ 2 ]