Get line number of the docstring.

        @param node_type: type of node_type
        @param node: node of currently checking
        @return: line number

def _getDocstringLineno(self, node_type, node):
        """
        Get line number of the docstring.

        @param node_type: type of node_type
        @param node: node of currently checking
        @return: line number
        """
        docstringStriped = node.as_string().strip()
        linenoDocstring = (node.lineno + docstringStriped
                           .count("\n", 0, docstringStriped.index('"""')))
        if node_type == "module":
            # Module starts from line 0.
            linenoDocstring += 1
        return linenoDocstring