@staticmethod<EOL><INDENT>def _check_conditional_statement(statement, num_collections):<DEDENT>
<EOL>correct_var = list(ascii_lowercase)[:num_collections]<EOL>st_statement = BaseCollection._remove_operators(statement)<EOL>parsed_st = [s for s in st_statement if s.isalpha()]<EOL>for var in parsed_st:<EOL><INDENT>if var not in correct_var:<EOL><INDENT>raise ValueError(<EOL>'<STR_LIT>'<EOL>'<STR_LIT>'<EOL>'<STR_LIT>'.format(<EOL>statement, '<STR_LIT:U+002CU+0020>'.join(correct_var))<EOL>)<EOL><DEDENT><DEDENT>return correct_var<EOL>
Method to check conditional statements to be sure that they are valid.

        Args:
            statement: A conditional statement as a string (e.g. a>25 and a%5==0).
                The variable should always be named as 'a' (without quotations).
            num_collections: An integer representing the number of data collections
                that the statement will be evaluating.

        Return:
            correct_var: A list of the correct variable names that should be
                used within the statement (eg. ['a', 'b', 'c'])