class_docstr: A class for representing multivariate rational function fields. 
docstr: Returns True if ``LC(a)`` is non-negative. 
code: def is_nonnegative(self, a):
      """Returns True if ``LC(a)`` is non-negative."""
      return self.domain.is_nonnegative(a.numer.LC)
  
imports: from sympy.polys.domains.compositedomain import CompositeDomain
  from sympy.polys.domains.field import Field
  from sympy.polys.polyerrors import CoercionFailed, GeneratorsError
  from sympy.utilities import public
label_desc: Use image node_id 28 for calling the FractionField obj's underlying member method code with example usage: obj.is_nonnegative(a) and returns: self