Looks at line 'i' for a subroutine or function definition.

def _match_exec(self, i):
        """Looks at line 'i' for a subroutine or function definition."""
        self.col_match = self.RE_EXEC.match(self._source[i])
        if self.col_match is not None:
            if self.col_match.group("codetype") == "function":
                self.el_type = Function
            else:
                self.el_type = Subroutine
            self.el_name = self.col_match.group("name")
        
            return True
        else:
            return False