'Create a new security group for your account.
This will create the security group within the region you
are currently connected to.
:type name: string
:param name: The name of the new security group
:type description: string
:param description: The description of the new security group
:type vpc_id: string
:param vpc_id: The ID of the VPC to create the security group in,
if any.
:type dry_run: bool
:param dry_run: Set to True if the operation should not actually run.
:rtype: :class:`boto.ec2.securitygroup.SecurityGroup`
:return: The newly created :class:`boto.ec2.securitygroup.SecurityGroup`.'

def create_security_group(self, name, description, vpc_id=None, dry_run=False):

    params = {'GroupName': name, 'GroupDescription': description}
    if (vpc_id is not None):
        params['VpcId'] = vpc_id
    if dry_run:
        params['DryRun'] = 'true'
    group = self.get_object('CreateSecurityGroup', params, SecurityGroup, verb='POST')
    group.name = name
    group.description = description
    if (vpc_id is not None):
        group.vpc_id = vpc_id
    return group
