'Updates a global index(es) in DynamoDB after the table has been created.
Requires a ``global_indexes`` parameter, which should be a
dictionary. If provided, it should specify the index name, which is also
a dict containing a ``read`` & ``write`` key, both of which
should have an integer value associated with them.
To update ``global_indexes`` information on the ``Table``, you\'ll need
to call ``Table.describe``.
Returns ``True`` on success.
Example::
# To update a global index
>>> users.update_global_secondary_index(global_indexes={
...     \'TheIndexNameHere\': {
...         \'read\': 15,
...         \'write\': 5,
True'

def update_global_secondary_index(self, global_indexes):

    if global_indexes:
        gsi_data = []
        for (gsi_name, gsi_throughput) in global_indexes.items():
            gsi_data.append({'Update': {'IndexName': gsi_name, 'ProvisionedThroughput': {'ReadCapacityUnits': int(gsi_throughput['read']), 'WriteCapacityUnits': int(gsi_throughput['write'])}}})
        self.connection.update_table(self.table_name, global_secondary_index_updates=gsi_data)
        return True
    else:
        msg = 'You    need    to    provide    the    global    indexes    to    update_global_secondary_index    method'
        boto.log.error(msg)
        return False
