'Set common instance metadata for the project. Common uses
are for setting \'sshKeys\', or setting a project-wide
\'startup-script\' for all nodes (instances).  Passing in
``None`` for the \'metadata\' parameter will clear out all common
instance metadata *except* for \'sshKeys\'. If you also want to
update \'sshKeys\', set the \'force\' parameter to ``True``.
:param  metadata: Dictionary of metadata. Can be either a standard
python dictionary, or the format expected by
GCE (e.g. {\'items\': [{\'key\': k1, \'value\': v1}, ...}]
:type   metadata: ``dict`` or ``None``
:param  force: Force update of \'sshKeys\'. If force is ``False`` (the
default), existing sshKeys will be retained. Setting
force to ``True`` will either replace sshKeys if a new
a new value is supplied, or deleted if no new value
is supplied.
:type   force: ``bool``
:return: True if successful
:rtype:  ``bool``'

def set_common_instance_metadata(self, metadata=None, force=False):

    return self.driver.ex_set_common_instance_metadata(self, metadata)
