Parses the line starting with global to extract all the valid meta key/value pair.

def parse_global_meta(self, global_meta_str):
        """
        Parses the line starting with global to extract all the valid meta key/value pair.
        """

        if global_meta_str:
            global_meta_str = regex_meta.findall(global_meta_str + ',')
        if global_meta_str:
            for par in global_meta_str:
                if par[0] is not '':
                    val1 = par[0].lower()
                    val2 = par[1]
                else:
                    val1 = par[2].lower()
                    val2 = par[3]
                val1 = val1.strip()
                val2 = val2.strip()
                if val1 in self.valid_global_keys :
                    if val1 in ('range', 'corr', 'labeloff'):
                        val2 = val2.split(",")
                        val2 = [x.strip() for x in val2 if x]
                    self.global_meta[val1] = val2
                else:
                    self._raise_error("'{0}' is not a valid global meta key".format(val1))