class_docstr: An (abstract) category.
  
  Explanation
  ===========
  
  A category [JoyOfCats] is a quadruple `\mbox{K} = (O, \hom, id,
  \circ)` consisting of
  
  * a (set-theoretical) class `O`, whose members are called
    `K`-objects,
  
  * for each pair `(A, B)` of `K`-objects, a set `\hom(A, B)` whose
    members are called `K`-morphisms from `A` to `B`,
  
  * for a each `K`-object `A`, a morphism `id:A\rightarrow A`,
    called the `K`-identity of `A`,
  
  * a composition law `\circ` associating with every `K`-morphisms
    `f:A\rightarrow B` and `g:B\rightarrow C` a `K`-morphism `g\circ
    f:A\rightarrow C`, called the composite of `f` and `g`.
  
  Composition is associative, `K`-identities are identities with
  respect to composition, and the sets `\hom(A, B)` are pairwise
  disjoint.
  
  This class knows nothing about its objects and morphisms.
  Concrete cases of (abstract) categories should be implemented as
  classes derived from this one.
  
  Certain instances of :class:`Diagram` can be asserted to be
  commutative in a :class:`Category` by supplying the argument
  ``commutative_diagrams`` in the constructor.
  
  Examples
  ========
  
  >>> from sympy.categories import Object, NamedMorphism, Diagram, Category
  >>> from sympy import FiniteSet
  >>> A = Object("A")
  >>> B = Object("B")
  >>> C = Object("C")
  >>> f = NamedMorphism(A, B, "f")
  >>> g = NamedMorphism(B, C, "g")
  >>> d = Diagram([f, g])
  >>> K = Category("K", commutative_diagrams=[d])
  >>> K.commutative_diagrams == FiniteSet(d)
  True
  
  See Also
  ========
  
  Diagram
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docstr: Returns the class of objects of this category.
  
  Examples
  ========
  
  >>> from sympy.categories import Object, Category
  >>> from sympy import FiniteSet
  >>> A = Object("A")
  >>> B = Object("B")
  >>> K = Category("K", FiniteSet(A, B))
  >>> K.objects
  Class({Object("A"), Object("B")})
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code: def objects(self):
      """
      Returns the class of objects of this category.
  
      Examples
      ========
  
      >>> from sympy.categories import Object, Category
      >>> from sympy import FiniteSet
      >>> A = Object("A")
      >>> B = Object("B")
      >>> K = Category("K", FiniteSet(A, B))
      >>> K.objects
      Class({Object("A"), Object("B")})
  
      """
      return self.args[1]
  
imports: from sympy.core import S, Basic, Dict, Symbol, Tuple, sympify
  from sympy.core.symbol import Str
  from sympy.sets import Set, FiniteSet, EmptySet
  from sympy.utilities.iterables import iterable
label_desc: Use image node_id 3 for calling the Category obj's underlying member method code with example usage: obj.objects() and returns: self