class_docstr: Set containing default assumptions which are applied to the ``ask()``
  function.
  
  Explanation
  ===========
  
  This is used to represent global assumptions, but you can also use this
  class to create your own local assumptions contexts. It is basically a thin
  wrapper to Python's set, so see its documentation for advanced usage.
  
  Examples
  ========
  
  The default assumption context is ``global_assumptions``, which is initially empty:
  
  >>> from sympy import ask, Q
  >>> from sympy.assumptions import global_assumptions
  >>> global_assumptions
  AssumptionsContext()
  
  You can add default assumptions:
  
  >>> from sympy.abc import x
  >>> global_assumptions.add(Q.real(x))
  >>> global_assumptions
  AssumptionsContext({Q.real(x)})
  >>> ask(Q.real(x))
  True
  
  And remove them:
  
  >>> global_assumptions.remove(Q.real(x))
  >>> print(ask(Q.real(x)))
  None
  
  The ``clear()`` method removes every assumption:
  
  >>> global_assumptions.add(Q.positive(x))
  >>> global_assumptions
  AssumptionsContext({Q.positive(x)})
  >>> global_assumptions.clear()
  >>> global_assumptions
  AssumptionsContext()
  
  See Also
  ========
  
  assuming
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code: def _sympystr(self, printer):
      if not self:
          return "%s()" % self.__class__.__name__
      return "{}({})".format(
          self.__class__.__name__, printer._print_set(self)
      )
  
imports: from contextlib import contextmanager
  import inspect
  from sympy.core.symbol import Str
  from sympy.core.sympify import _sympify
  from sympy.logic.boolalg import Boolean, false, true
  from sympy.multipledispatch.dispatcher import Dispatcher, str_signature
  from sympy.utilities.exceptions import sympy_deprecation_warning
  from sympy.utilities.iterables import is_sequence
  from sympy.utilities.source import get_class
label_desc: Use image node_id 2 for calling the AssumptionsContext obj's underlying member method code with example usage: obj._sympystr(printer) and returns: str, unknown