'Consumes a + or - character if part of a number in sci. notation.
Returns True if the character was consumed and self.offset was
updated, False otherwise.'

def check_scientific_notation(self):

    curr_char = self.formula[self.offset]
    if ((curr_char in '+-') and (len(self.token) >= 1) and self.SN_RE.match(''.join(self.token))):
        self.token.append(curr_char)
        self.offset += 1
        return True
    return False
