redefining global symbol: pi when processing file

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<robot <a="" href="http://xmlns:xacro="http://www.ros.org/wiki/xacro%22">xmlns:xacro="http://www.ros.org/wiki/...></robot>

  <!-- transmission -->
  <xacro:include filename="$(find tm_grasp_description)/urdf/tm.transmission.xacro" />

  <!-- Mass parameters -->
  <xacro:property name="pi" value="3.14159265" />

  <xacro:property name="base_mass" value="1.0" />
  <xacro:property name="shoulder_mass" value="4.5" />
  <xacro:property name="arm_1_mass" value="10.5" />
  <xacro:property name="arm_2_mass" value="2.1" />
  <xacro:property name="wrist_1_mass" value="1.45" />
  <xacro:property name="wrist_2_mass" value="1.45" />
  <xacro:property name="wrist_3_mass" value="0.4" />

  <!-- Kinematic model -->
  <!-- Properties from tmcontrol.conf -->
  <!--
    DH for TM700:
    a = [0.00000, 0.329, 0.3115,  0.00000,  0.00000,  0.0000]
    d = [0.1451,  0.00000,  0.00000,  -0.1222,  0.106,  0.1144]
    alpha = [ -1.570796327, 0, 0, 1.570796327, 1.570796327, 0 ]
    q_home_offset = [0, -1.570796327, 0, 1.570796327, 0, 0]
    joint_direction = [-1, -1, 1, -1, 1, 1]
    mass = [4.5, 10.5, 2.1, 1.45, 1.45, 0.4]
    center_of_mass = [ [0, -0.02561, 0.00193], [0.2125, 0, 0.11336], [0.11993, 0.0, 0.0265], [0, -0.0018, 0.01634], [0, 0.0018,0.01634], [0, 0, -0.001159] ](tm700)
  -->
  <xacro:property name="tm_d1" value="0.1451" />
  <xacro:property name="tm_a2" value="0.3290" />
  <xacro:property name="tm_a3" value="0.3115" />
  <xacro:property name="tm_d4" value="0.1222" />
  <xacro:property name="tm_d5" value="0.1060" />
  <xacro:property name="tm_d6" value="0.1144" />

  <!-- offsets for shoulder/elbow joints -->
  <xacro:property name="shoulder_offset" value="-0.146" />  <!-- measured from model -->
  <xacro:property name="elbow_offset" value="0.1298" /> <!-- measured from model -->       
  <xacro:property name="wrist_offset" value="${-tm_d4 - elbow_offset - shoulder_offset}" />

  <!-- link lengths used in model -->
  <xacro:property name="shoulder_height" value="${tm_d1}" />
  <xacro:property name="arm_1_length" value="${tm_a2}" />
  <xacro:property name="arm_2_length" value="${tm_a3}" />
  <xacro:property name="wrist_1_length" value="tm_d5}" />
  <xacro:property name="wrist_2_length" value="${tm_d5}" />
  <xacro:property name="wrist_3_length" value="0.0565" />
  <xacro:property name="ee_length" value="${tm_d6 - wrist_3_length}" />

  <xacro:macro name="cylinder_inertial" params="radius length mass *origin">
    <inertial>
      <mass value="${mass}" />
      <xacro:insert_block name="origin" />
      <inertia ixx="${0.0833333 * mass * (3 * radius * radius + length * length)}" ixy="0.0" ixz="0.0"
        iyy="${0.0833333 * mass * (3 * radius * radius + length * length)}" iyz="0.0"
        izz="${0.5 * mass * radius * radius}" />
    </inertial>
  </xacro:macro>

  <xacro:macro name="tm700_robot" params="prefix joint_limited">

    <!-- transmission prefix -->
    <xacro:tm_arm_transmission prefix="${prefix}" />

    <link name="${prefix}base_link" >
      <visual>
        <geometry>
      <mesh filename="package://tm_grasp_description/meshes/tm700/visual/Base.STL" />
        </geometry>
        <material name="Grey">
          <color rgba="0.5 0.5 0.5 1.0"/>
        </material>
      </visual>
      <collision>
        <geometry>
      <mesh filename="package://tm_grasp_description/meshes/tm700/collision/base.STL" />
        </geometry>
      </collision>

      <xacro:cylinder_inertial radius="0.06" length ...