prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  Parameters needs examples in the documentation
  ### What is the expected enhancement?
  
  Many users land in https://qiskit.org/documentation/stubs/qiskit.circuit.Parameter.html  when search on how to parametrize circuits. @Cryoris did a good jobs at explaining them in https://quantumcomputing.stackexchange.com/questions/13558/how-to-add-several-parameters-in-qiskit-circuit . I think the Parameter docstring needs a short example.
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `qiskit/circuit/parameter.py`
  Content:
  ```
  1 # This code is part of Qiskit.
  2 #
  3 # (C) Copyright IBM 2017, 2019.
  4 #
  5 # This code is licensed under the Apache License, Version 2.0. You may
  6 # obtain a copy of this license in the LICENSE.txt file in the root directory
  7 # of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
  8 #
  9 # Any modifications or derivative works of this code must retain this
  10 # copyright notice, and modified files need to carry a notice indicating
  11 # that they have been altered from the originals.
  12 """
  13 Parameter Class for variable parameters.
  14 """
  15 
  16 from uuid import uuid4
  17 
  18 from .parameterexpression import ParameterExpression
  19 
  20 try:
  21     import symengine
  22 
  23     HAS_SYMENGINE = True
  24 except ImportError:
  25     HAS_SYMENGINE = False
  26 
  27 
  28 class Parameter(ParameterExpression):
  29     """Parameter Class for variable parameters."""
  30 
  31     def __new__(cls, name, uuid=None):  # pylint: disable=unused-argument
  32         # Parameter relies on self._uuid being set prior to other attributes
  33         # (e.g. symbol_map) which may depend on self._uuid for Parameter's hash
  34         # or __eq__ functions.
  35         obj = object.__new__(cls)
  36 
  37         if uuid is None:
  38             obj._uuid = uuid4()
  39         else:
  40             obj._uuid = uuid
  41 
  42         obj._hash = hash(obj._uuid)
  43         return obj
  44 
  45     def __getnewargs__(self):
  46         # Unpickling won't in general call __init__ but will always call
  47         # __new__. Specify arguments to be passed to __new__ when unpickling.
  48 
  49         return (self.name, self._uuid)
  50 
  51     def __init__(self, name: str):
  52         """Create a new named :class:`Parameter`.
  53 
  54         Args:
  55             name: name of the ``Parameter``, used for visual representation. This can
  56                 be any unicode string, e.g. "ϕ".
  57         """
  58         self._name = name
  59         if not HAS_SYMENGINE:
  60             from sympy import Symbol
  61 
  62             symbol = Symbol(name)
  63         else:
  64             symbol = symengine.Symbol(name)
  65         super().__init__(symbol_map={self: symbol}, expr=symbol)
  66 
  67     def subs(self, parameter_map: dict):
  68         """Substitute self with the corresponding parameter in ``parameter_map``."""
  69         return parameter_map[self]
  70 
  71     @property
  72     def name(self):
  73         """Returns the name of the :class:`Parameter`."""
  74         return self._name
  75 
  76     def __str__(self):
  77         return self.name
  78 
  79     def __copy__(self):
  80         return self
  81 
  82     def __deepcopy__(self, memo=None):
  83         return self
  84 
  85     def __repr__(self):
  86         return f"{self.__class__.__name__}({self.name})"
  87 
  88     def __eq__(self, other):
  89         if isinstance(other, Parameter):
  90             return self._uuid == other._uuid
  91         elif isinstance(other, ParameterExpression):
  92             return super().__eq__(other)
  93         else:
  94             return False
  95 
  96     def __hash__(self):
  97         return self._hash
  98 
  99     def __getstate__(self):
  100         return {"name": self._name}
  101 
  102     def __setstate__(self, state):
  103         self._name = state["name"]
  104         if not HAS_SYMENGINE:
  105             from sympy import Symbol
  106 
  107             symbol = Symbol(self._name)
  108         else:
  109             symbol = symengine.Symbol(self._name)
  110         super().__init__(symbol_map={self: symbol}, expr=symbol)
  111
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
golden_diff: diff --git a/qiskit/circuit/parameter.py b/qiskit/circuit/parameter.py
  --- a/qiskit/circuit/parameter.py
  +++ b/qiskit/circuit/parameter.py
  @@ -26,7 +26,32 @@
   
   
   class Parameter(ParameterExpression):
  -    """Parameter Class for variable parameters."""
  +    """Parameter Class for variable parameters.
  +
  +    A parameter is a variable value that is not required to be fixed
  +    at circuit definition.
  +
  +    Examples:
  +
  +        Construct a variable-rotation X gate using circuit parameters.
  +
  +        .. jupyter-execute::
  +
  +            from qiskit.circuit import QuantumCircuit, Parameter
  +
  +            # create the parameter
  +            phi = Parameter('phi')
  +            qc = QuantumCircuit(1)
  +
  +            # parameterize the rotation
  +            qc.rx(phi, 0)
  +            qc.draw()
  +
  +            # bind the parameters after circuit to create a bound circuit
  +            bc = qc.bind_parameters({phi: 3.14})
  +            bc.measure_all()
  +            bc.draw()
  +    """
   
       def __new__(cls, name, uuid=None):  # pylint: disable=unused-argument
           # Parameter relies on self._uuid being set prior to other attributes
  
verification_info: {"golden_diff": "diff --git a/qiskit/circuit/parameter.py b/qiskit/circuit/parameter.py\n--- a/qiskit/circuit/parameter.py\n+++ b/qiskit/circuit/parameter.py\n@@ -26,7 +26,32 @@\n \n \n class Parameter(ParameterExpression):\n-    \"\"\"Parameter Class for variable parameters.\"\"\"\n+    \"\"\"Parameter Class for variable parameters.\n+\n+    A parameter is a variable value that is not required to be fixed\n+    at circuit definition.\n+\n+    Examples:\n+\n+        Construct a variable-rotation X gate using circuit parameters.\n+\n+        .. jupyter-execute::\n+\n+            from qiskit.circuit import QuantumCircuit, Parameter\n+\n+            # create the parameter\n+            phi = Parameter('phi')\n+            qc = QuantumCircuit(1)\n+\n+            # parameterize the rotation\n+            qc.rx(phi, 0)\n+            qc.draw()\n+\n+            # bind the parameters after circuit to create a bound circuit\n+            bc = qc.bind_parameters({phi: 3.14})\n+            bc.measure_all()\n+            bc.draw()\n+    \"\"\"\n \n     def __new__(cls, name, uuid=None):  # pylint: disable=unused-argument\n         # Parameter relies on self._uuid being set prior to other attributes\n", "issue": "Parameters needs examples in the documentation\n### What is the expected enhancement?\n\nMany users land in https://qiskit.org/documentation/stubs/qiskit.circuit.Parameter.html  when search on how to parametrize circuits. @Cryoris did a good jobs at explaining them in https://quantumcomputing.stackexchange.com/questions/13558/how-to-add-several-parameters-in-qiskit-circuit . I think the Parameter docstring needs a short example.\n", "before_files": [{"content": "# This code is part of Qiskit.\n#\n# (C) Copyright IBM 2017, 2019.\n#\n# This code is licensed under the Apache License, Version 2.0. You may\n# obtain a copy of this license in the LICENSE.txt file in the root directory\n# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.\n#\n# Any modifications or derivative works of this code must retain this\n# copyright notice, and modified files need to carry a notice indicating\n# that they have been altered from the originals.\n\"\"\"\nParameter Class for variable parameters.\n\"\"\"\n\nfrom uuid import uuid4\n\nfrom .parameterexpression import ParameterExpression\n\ntry:\n    import symengine\n\n    HAS_SYMENGINE = True\nexcept ImportError:\n    HAS_SYMENGINE = False\n\n\nclass Parameter(ParameterExpression):\n    \"\"\"Parameter Class for variable parameters.\"\"\"\n\n    def __new__(cls, name, uuid=None):  # pylint: disable=unused-argument\n        # Parameter relies on self._uuid being set prior to other attributes\n        # (e.g. symbol_map) which may depend on self._uuid for Parameter's hash\n        # or __eq__ functions.\n        obj = object.__new__(cls)\n\n        if uuid is None:\n            obj._uuid = uuid4()\n        else:\n            obj._uuid = uuid\n\n        obj._hash = hash(obj._uuid)\n        return obj\n\n    def __getnewargs__(self):\n        # Unpickling won't in general call __init__ but will always call\n        # __new__. Specify arguments to be passed to __new__ when unpickling.\n\n        return (self.name, self._uuid)\n\n    def __init__(self, name: str):\n        \"\"\"Create a new named :class:`Parameter`.\n\n        Args:\n            name: name of the ``Parameter``, used for visual representation. This can\n                be any unicode string, e.g. \"\u03d5\".\n        \"\"\"\n        self._name = name\n        if not HAS_SYMENGINE:\n            from sympy import Symbol\n\n            symbol = Symbol(name)\n        else:\n            symbol = symengine.Symbol(name)\n        super().__init__(symbol_map={self: symbol}, expr=symbol)\n\n    def subs(self, parameter_map: dict):\n        \"\"\"Substitute self with the corresponding parameter in ``parameter_map``.\"\"\"\n        return parameter_map[self]\n\n    @property\n    def name(self):\n        \"\"\"Returns the name of the :class:`Parameter`.\"\"\"\n        return self._name\n\n    def __str__(self):\n        return self.name\n\n    def __copy__(self):\n        return self\n\n    def __deepcopy__(self, memo=None):\n        return self\n\n    def __repr__(self):\n        return f\"{self.__class__.__name__}({self.name})\"\n\n    def __eq__(self, other):\n        if isinstance(other, Parameter):\n            return self._uuid == other._uuid\n        elif isinstance(other, ParameterExpression):\n            return super().__eq__(other)\n        else:\n            return False\n\n    def __hash__(self):\n        return self._hash\n\n    def __getstate__(self):\n        return {\"name\": self._name}\n\n    def __setstate__(self, state):\n        self._name = state[\"name\"]\n        if not HAS_SYMENGINE:\n            from sympy import Symbol\n\n            symbol = Symbol(self._name)\n        else:\n            symbol = symengine.Symbol(self._name)\n        super().__init__(symbol_map={self: symbol}, expr=symbol)\n", "path": "qiskit/circuit/parameter.py"}], "after_files": [{"content": "# This code is part of Qiskit.\n#\n# (C) Copyright IBM 2017, 2019.\n#\n# This code is licensed under the Apache License, Version 2.0. You may\n# obtain a copy of this license in the LICENSE.txt file in the root directory\n# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.\n#\n# Any modifications or derivative works of this code must retain this\n# copyright notice, and modified files need to carry a notice indicating\n# that they have been altered from the originals.\n\"\"\"\nParameter Class for variable parameters.\n\"\"\"\n\nfrom uuid import uuid4\n\nfrom .parameterexpression import ParameterExpression\n\ntry:\n    import symengine\n\n    HAS_SYMENGINE = True\nexcept ImportError:\n    HAS_SYMENGINE = False\n\n\nclass Parameter(ParameterExpression):\n    \"\"\"Parameter Class for variable parameters.\n\n    A parameter is a variable value that is not required to be fixed\n    at circuit definition.\n\n    Examples:\n\n        Construct a variable-rotation X gate using circuit parameters.\n\n        .. jupyter-execute::\n\n            from qiskit.circuit import QuantumCircuit, Parameter\n\n            # create the parameter\n            phi = Parameter('phi')\n            qc = QuantumCircuit(1)\n\n            # parameterize the rotation\n            qc.rx(phi, 0)\n            qc.draw()\n\n            # bind the parameters after circuit to create a bound circuit\n            bc = qc.bind_parameters({phi: 3.14})\n            bc.measure_all()\n            bc.draw()\n    \"\"\"\n\n    def __new__(cls, name, uuid=None):  # pylint: disable=unused-argument\n        # Parameter relies on self._uuid being set prior to other attributes\n        # (e.g. symbol_map) which may depend on self._uuid for Parameter's hash\n        # or __eq__ functions.\n        obj = object.__new__(cls)\n\n        if uuid is None:\n            obj._uuid = uuid4()\n        else:\n            obj._uuid = uuid\n\n        obj._hash = hash(obj._uuid)\n        return obj\n\n    def __getnewargs__(self):\n        # Unpickling won't in general call __init__ but will always call\n        # __new__. Specify arguments to be passed to __new__ when unpickling.\n\n        return (self.name, self._uuid)\n\n    def __init__(self, name: str):\n        \"\"\"Create a new named :class:`Parameter`.\n\n        Args:\n            name: name of the ``Parameter``, used for visual representation. This can\n                be any unicode string, e.g. \"\u03d5\".\n        \"\"\"\n        self._name = name\n        if not HAS_SYMENGINE:\n            from sympy import Symbol\n\n            symbol = Symbol(name)\n        else:\n            symbol = symengine.Symbol(name)\n        super().__init__(symbol_map={self: symbol}, expr=symbol)\n\n    def subs(self, parameter_map: dict):\n        \"\"\"Substitute self with the corresponding parameter in ``parameter_map``.\"\"\"\n        return parameter_map[self]\n\n    @property\n    def name(self):\n        \"\"\"Returns the name of the :class:`Parameter`.\"\"\"\n        return self._name\n\n    def __str__(self):\n        return self.name\n\n    def __copy__(self):\n        return self\n\n    def __deepcopy__(self, memo=None):\n        return self\n\n    def __repr__(self):\n        return f\"{self.__class__.__name__}({self.name})\"\n\n    def __eq__(self, other):\n        if isinstance(other, Parameter):\n            return self._uuid == other._uuid\n        elif isinstance(other, ParameterExpression):\n            return super().__eq__(other)\n        else:\n            return False\n\n    def __hash__(self):\n        return self._hash\n\n    def __getstate__(self):\n        return {\"name\": self._name}\n\n    def __setstate__(self, state):\n        self._name = state[\"name\"]\n        if not HAS_SYMENGINE:\n            from sympy import Symbol\n\n            symbol = Symbol(self._name)\n        else:\n            symbol = symengine.Symbol(self._name)\n        super().__init__(symbol_map={self: symbol}, expr=symbol)\n", "path": "qiskit/circuit/parameter.py"}]}