feat: add quantifier entity

src/entity/quantifiers.py

@@ -0,0 +1,24 @@
+from src.entity.base import Base
+from src.entity.operators import *
+
+class Quantifier(Base):
+    symbol = ''
+
+    def __init__(self, expr):
+        self.expr = expr
+
+        self._expr = f'({self.expr})' if isinstance(self.expr, Operator) else str(self.expr)
+
+    def __str__(self):
+        return f'{self.symbol}{self._expr}'
+
+class Universal(Quantifier):
+    symbol = '∀x'
+
+class Existential(Quantifier):
+    symbol = '∃x'
+
+quantifiers = {
+    "Ax": Universal,
+    "Ex": Existential
+}