prompt: You will be provided with a partial code base and an issue statement explaining a problem to resolve.
  <issue>
  [PS-1]Add new RPC services definition in elasticdl.proto according to PS design
  [PS design](https://github.com/sql-machine-learning/elasticdl/blob/develop/docs/designs/ps_design.md#rpc-definition) adds some new RPC services.
  
  </issue>
  <code>
  [start of elasticdl/python/ps/servicer.py]
  1 from google.protobuf import empty_pb2
  2 
  3 from elasticdl.proto import elasticdl_pb2_grpc
  4 
  5 
  6 class PserverServicer(elasticdl_pb2_grpc.PserverServicer):
  7     """PS service implementation"""
  8 
  9     def __init__(
  10         self,
  11         parameters,
  12         grads_to_wait,
  13         optimizer,
  14         lr_staleness_modulation=False,
  15         use_async=False,
  16     ):
  17         self._parameters = parameters
  18         self._grads_to_wait = grads_to_wait
  19         self._optimizer = optimizer
  20         self._lr_staleness_modulation = lr_staleness_modulation
  21         self._use_async = use_async
  22         self._version = 0
  23 
  24     def pull_variable(self, request, _):
  25         # TODO: implement this RPC service
  26         return empty_pb2.Empty()
  27 
  28     def pull_embedding_vector(self, request, _):
  29         # TODO: implement this RPC service
  30         return empty_pb2.Empty()
  31 
  32     def push_model(self, request, _):
  33         # TODO: implement this RPC service
  34         return empty_pb2.Empty()
  35 
  36     def push_gradient(self, request, _):
  37         # TODO: implement this RPC service
  38         return empty_pb2.Empty()
  39
  [end of elasticdl/python/ps/servicer.py]
  </code>
  
  I need you to solve this issue by generating a single patch file that I can apply directly to this repository using git apply. Please respond with a single patch file in the following format.
  <patch>
  diff --git a/file.py b/file.py
  --- a/file.py
  +++ b/file.py
  @@ -1,27 +1,35 @@
   def euclidean(a, b):
  -    while b:
  -        a, b = b, a % b
  -    return a
  +    if b == 0:
  +        return a
  +    return euclidean(b, a % b)
   
   
   def bresenham(x0, y0, x1, y1):
       points = []
       dx = abs(x1 - x0)
       dy = abs(y1 - y0)
  -    sx = 1 if x0 < x1 else -1
  -    sy = 1 if y0 < y1 else -1
  -    err = dx - dy
  +    x, y = x0, y0
  +    sx = -1 if x0 > x1 else 1
  +    sy = -1 if y0 > y1 else 1
   
  -    while True:
  -        points.append((x0, y0))
  -        if x0 == x1 and y0 == y1:
  -            break
  -        e2 = 2 * err
  -        if e2 > -dy:
  -            err -= dy
  -            x0 += sx
  -        if e2 < dx:
  -            err += dx
  -            y0 += sy
  +    if dx > dy:
  +        err = dx / 2.0
  +        while x != x1:
  +            points.append((x, y))
  +            err -= dy
  +            if err < 0:
  +                y += sy
  +                err += dx
  +            x += sx
  +    else:
  +        err = dy / 2.0
  +        while y != y1:
  +            points.append((x, y))
  +            err -= dx
  +            if err < 0:
  +                x += sx
  +                err += dy
  +            y += sy
  +
  +    points.append((x, y))
       return points
  
  </patch>
golden_diff: diff --git a/elasticdl/python/ps/servicer.py b/elasticdl/python/ps/servicer.py
  --- a/elasticdl/python/ps/servicer.py
  +++ b/elasticdl/python/ps/servicer.py
  @@ -1,6 +1,6 @@
   from google.protobuf import empty_pb2
   
  -from elasticdl.proto import elasticdl_pb2_grpc
  +from elasticdl.proto import elasticdl_pb2, elasticdl_pb2_grpc
   
   
   class PserverServicer(elasticdl_pb2_grpc.PserverServicer):
  @@ -23,11 +23,11 @@
   
       def pull_variable(self, request, _):
           # TODO: implement this RPC service
  -        return empty_pb2.Empty()
  +        return elasticdl_pb2.PullVariableResponse()
   
       def pull_embedding_vector(self, request, _):
           # TODO: implement this RPC service
  -        return empty_pb2.Empty()
  +        return elasticdl_pb2.Tensor()
   
       def push_model(self, request, _):
           # TODO: implement this RPC service
  @@ -35,4 +35,4 @@
   
       def push_gradient(self, request, _):
           # TODO: implement this RPC service
  -        return empty_pb2.Empty()
  +        return elasticdl_pb2.PushGradientResponse()
  
verification_info: {"golden_diff": "diff --git a/elasticdl/python/ps/servicer.py b/elasticdl/python/ps/servicer.py\n--- a/elasticdl/python/ps/servicer.py\n+++ b/elasticdl/python/ps/servicer.py\n@@ -1,6 +1,6 @@\n from google.protobuf import empty_pb2\n \n-from elasticdl.proto import elasticdl_pb2_grpc\n+from elasticdl.proto import elasticdl_pb2, elasticdl_pb2_grpc\n \n \n class PserverServicer(elasticdl_pb2_grpc.PserverServicer):\n@@ -23,11 +23,11 @@\n \n     def pull_variable(self, request, _):\n         # TODO: implement this RPC service\n-        return empty_pb2.Empty()\n+        return elasticdl_pb2.PullVariableResponse()\n \n     def pull_embedding_vector(self, request, _):\n         # TODO: implement this RPC service\n-        return empty_pb2.Empty()\n+        return elasticdl_pb2.Tensor()\n \n     def push_model(self, request, _):\n         # TODO: implement this RPC service\n@@ -35,4 +35,4 @@\n \n     def push_gradient(self, request, _):\n         # TODO: implement this RPC service\n-        return empty_pb2.Empty()\n+        return elasticdl_pb2.PushGradientResponse()\n", "issue": "[PS-1]Add new RPC services definition in elasticdl.proto according to PS design\n[PS design](https://github.com/sql-machine-learning/elasticdl/blob/develop/docs/designs/ps_design.md#rpc-definition) adds some new RPC services.\n", "before_files": [{"content": "from google.protobuf import empty_pb2\n\nfrom elasticdl.proto import elasticdl_pb2_grpc\n\n\nclass PserverServicer(elasticdl_pb2_grpc.PserverServicer):\n    \"\"\"PS service implementation\"\"\"\n\n    def __init__(\n        self,\n        parameters,\n        grads_to_wait,\n        optimizer,\n        lr_staleness_modulation=False,\n        use_async=False,\n    ):\n        self._parameters = parameters\n        self._grads_to_wait = grads_to_wait\n        self._optimizer = optimizer\n        self._lr_staleness_modulation = lr_staleness_modulation\n        self._use_async = use_async\n        self._version = 0\n\n    def pull_variable(self, request, _):\n        # TODO: implement this RPC service\n        return empty_pb2.Empty()\n\n    def pull_embedding_vector(self, request, _):\n        # TODO: implement this RPC service\n        return empty_pb2.Empty()\n\n    def push_model(self, request, _):\n        # TODO: implement this RPC service\n        return empty_pb2.Empty()\n\n    def push_gradient(self, request, _):\n        # TODO: implement this RPC service\n        return empty_pb2.Empty()\n", "path": "elasticdl/python/ps/servicer.py"}]}