'Look for rdata with the specified name and type in the zone,
and return an rdataset encapsulating it.
The I{name}, I{rdtype}, and I{covers} parameters may be
strings, in which case they will be converted to their proper
type.
The rdataset returned is not a copy; changes to it will change
the zone.
None is returned if the name or type are not found.
Use L{find_rdataset} if you want to have KeyError raised instead.
@param name: the owner name to look for
@type name: DNS.name.Name object or string
@param rdtype: the rdata type desired
@type rdtype: int or string
@param covers: the covered type (defaults to None)
@type covers: int or string
@param create: should the node and rdataset be created if they do not
exist?
@type create: bool
@rtype: dns.rrset.RRset object'

def get_rdataset(self, name, rdtype, covers=dns.rdatatype.NONE, create=False):

    try:
        rdataset = self.find_rdataset(name, rdtype, covers, create)
    except KeyError:
        rdataset = None
    return rdataset
