class_docstr: A class for representing rational function fields. 
class_docstr_tok: ["A","class","for","representing","rational","function","fields","."]
docstr: Returns denominator of ``a``. 
docstr_tok: ["Returns","denominator","of","``","a","``","."]
code: def denom(self, a):
      """Returns denominator of ``a``."""
      return a.denom()
  
imports: from sympy.polys.domains.field import Field
  from sympy.polys.domains.compositedomain import CompositeDomain
  from sympy.polys.polyclasses import DMF
  from sympy.polys.polyerrors import GeneratorsNeeded
  from sympy.polys.polyutils import dict_from_basic, basic_from_dict, _dict_reorder
  from sympy.utilities import public
label_desc: Use image node_id 25 for calling the FractionField obj's underlying member method code with example usage: obj.denom(a) and returns: a