Extract a section element from an Rd object or Rd fragment.
an Rd object or fragment
the required section, a string
If the class or the "Rd_tag" attribute of
rdo is "Rd" the
required section is extracted. Otherwise, if this attribute is equal to
rdo is returned.
In all other cases it is assumed that
rdo is the contents of
the required section, its "Rd_tag" attribute is set to
returned without further modification.
An Rd fragment for use as a section element of an Rd object
This function is intended for use by other functions which work with Rd objects.
Georgi N. Boshnakov