parameters: (input_handler)
return_statement: return IfStmt(test_expr, then_stmt, else_stmt)
docstring: Parse an if statement
docstring_summary: Parse an if statement
docstring_tokens: Parse an if statement
function: def parse_if_stmt(input_handler):
      """Parse an if statement"""
      input_handler.expect_ws('(')
      test_expr = parse_expr(input_handler)
      input_handler.expect(')')
      then_stmt = parse_stmt(input_handler)
      else_stmt = BlockStmt([])
      if input_handler.match_kw("else"):
          else_stmt = parse_stmt(input_handler)
      return IfStmt(test_expr, then_stmt, else_stmt)
function_tokens: def parse_if_stmt ( input_handler ) : input_handler . expect_ws ( '(' ) test_expr = parse_expr ( input_handler ) input_handler . expect ( ')' ) then_stmt = parse_stmt ( input_handler ) else_stmt = BlockStmt ( [ ] ) if input_handler . match_kw ( "else" ) : else_stmt = parse_stmt ( input_handler ) return IfStmt ( test_expr , then_stmt , else_stmt )